diff --git a/README.md b/README.md
index 0eac3097..32d25ca7 100644
--- a/README.md
+++ b/README.md
@@ -112,8 +112,8 @@ You can tweak the generated parser with several options:
   parser object is assigned to when no module loader is detected
 - `--extra-options <options>` — additional options (in JSON format, as an
   object) to pass to `peg.generate`
-- `--extra-options-file <file>` — file with additional options (in JSON
-  format, as an object) to pass to `peg.generate`
+- `-c`, `--extra-options-file <file>` — file with additional options (in JSON
+  or commonjs module format, as an object) to pass to `peg.generate`
 - `--format <format>` — format of the generated parser: `amd`, `es`, `commonjs`,
   `globals`, `umd` (default: `commonjs`)
 - `-o`, `--output <file>` - file to send output to.  Defaults to input file
@@ -128,6 +128,28 @@ You can tweak the generated parser with several options:
 - `-v`, `--version` - output the version number
 - `-h`, `--help` - display help for command
 
+If you specify options using `-c <file>` or `--extra-options-file <file>`, you
+will need to ensure you are using the correct types.  In particular, you may
+specify "plugin" as a string, or "plugins" as an array of objects that have a
+`use` method.  Always use the long (two-dash) form of the option.  Options
+that contain dashes should be specified in camel case. You may also specify an
+"input" field instead of using the command line.
+
+For example:
+
+```js
+// config.js or config.cjs
+module.exports = {
+  allowedStartRules = ["foo", "bar"],
+  format: "umd",
+  exportVar: "foo",
+  input: "fooGrammar.peggy",
+  plugins: [require("./plugin.js")],
+  testFile: "myTestInput.foo",
+  trace: true
+};
+```
+
 ### JavaScript API
 
 In Node.js, require the Peggy parser generator module:
diff --git a/bin/peggy.js b/bin/peggy.js
index 09e410f3..a734aa1a 100755
--- a/bin/peggy.js
+++ b/bin/peggy.js
@@ -2237,6 +2237,8 @@ function incrementNodeInspectorPort(args) {
 
 const MODULE_FORMATS = ["amd", "commonjs", "es", "globals", "umd"];
 const MODULE_FORMATS_WITH_DEPS = ["amd", "commonjs", "es", "umd"];
+const DEFAULT_FORMAT = "COMMON_JS";
+let verbose = false;
 
 // Helpers
 
@@ -2245,6 +2247,22 @@ function abort(message) {
   process.exit(1);
 }
 
+function abortError(msg, error) {
+  console.error(msg);
+  if (typeof error.format === "function") {
+    abort(error.format([{
+      source: testGrammarSource,
+      text: testText,
+    }]));
+  } else {
+    if (verbose) {
+      abort(error);
+    } else {
+      abort(`Error: ${error.message}`);
+    }
+  }
+}
+
 function addExtraOptions(options, json) {
   let extraOptions;
 
@@ -2253,7 +2271,7 @@ function addExtraOptions(options, json) {
   } catch (e) {
     if (!(e instanceof SyntaxError)) { throw e; }
 
-    abort("Error parsing JSON: " + e.message);
+    abortError("Error parsing JSON:", e);
   }
   if ((extraOptions === null)
       || (typeof extraOptions !== "object")
@@ -2263,12 +2281,20 @@ function addExtraOptions(options, json) {
   return Object.assign({}, options, extraOptions);
 }
 
+// Files
+
+function readStream(inputStream, callback) {
+  let input = "";
+  inputStream.on("data", data => { input += data; });
+  inputStream.on("end", () => { callback(input); });
+}
+
 function readFile(name) {
   let f = null;
   try {
     f = fs__default['default'].readFileSync(name, "utf8");
   } catch (e) {
-    abort(`Can't read from file "${name}".`);
+    abortError(`Can't read from file "${name}".`, e);
   }
   return f;
 }
@@ -2276,7 +2302,7 @@ function readFile(name) {
 // Command line processing
 
 const program = new commander.exports.Command();
-const options = program
+let options = program
   .version(peg__default['default'].VERSION, "-v, --version")
   .arguments("[input_file]")
   .addOption(
@@ -2306,9 +2332,15 @@ const options = program
     (val, prev) => addExtraOptions(prev, val)
   )
   .option(
-    "--extra-options-file <file>",
-    "file with additional options (in JSON format as an object) to pass to peg.generate",
-    (val, prev) => addExtraOptions(prev, readFile(val))
+    "-c, --extra-options-file <file>",
+    "file with additional options (in JSON or commonjs module format as an object) to pass to peg.generate",
+    (val, prev) => {
+      if (/\.c?js$/.test(val)) {
+        return Object.assign({}, prev, require(path__default['default'].resolve(val)));
+      } else {
+        return addExtraOptions(prev, readFile(val));
+      }
+    }
   )
   .addOption(
     new commander.exports.Option(
@@ -2316,7 +2348,7 @@ const options = program
       "format of the generated parser"
     )
       .choices(MODULE_FORMATS)
-      .default("commonjs")
+      .default(DEFAULT_FORMAT, '"commonjs"')
   )
   .option("-o, --output <file>", "output file")
   .option(
@@ -2342,7 +2374,6 @@ const options = program
   .addOption(
     new commander.exports.Option("-O, --optimize <style>")
       .hideHelp()
-      .default("speed")
       .argParser(() => {
         console.error("Option --optimize is deprecated from 1.2.0 and has no effect anymore.");
         console.error("It will be deleted in 2.0.");
@@ -2357,22 +2388,36 @@ if (options.extraOptions) {
   Object.assign(options, options.extraOptions);
   delete options.extraOptions;
 }
-if (options.extraOptionsFile) {
-  Object.assign(options, options.extraOptionsFile);
-  delete options.extraOptionsFile;
-}
-
-const verbose = options.verbose;
-delete options.verbose;
 
+// Ensure defaults do not clobber config file
 if (options.allowedStartRules.length === 0) {
   // [] is an invalid input, as is null
   // undefined doesn't work as a default in commander
   delete options.allowedStartRules;
 }
 
+if (options.extraOptionsFile) {
+  // Ensure defaults do not clobber config file
+  const fmt = options.format;
+  delete options.format;
+
+  // Command line overwrites config file
+  options = Object.assign({}, options.extraOptionsFile, options);
+  delete options.extraOptionsFile;
+
+  if (fmt !== DEFAULT_FORMAT) {
+    options.format = fmt;
+  }
+}
+if (!options.format || (options.format === DEFAULT_FORMAT)) {
+  options.format = "commonjs";
+}
+
+verbose = Boolean(options.verbose);
+delete options.verbose;
+
 if (options.plugin) {
-  options.plugins = options.plugin.map(val => {
+  options.plugins = (options.plugins || []).concat(options.plugin.map(val => {
     // If this is an absolute or relative path (not a module name)
     const id = (path__default['default'].isAbsolute(val) || /^\.\.?[/\\]/.test(val))
       ? path__default['default'].resolve(val)
@@ -2382,10 +2427,10 @@ if (options.plugin) {
       mod = require(id);
     } catch (e) {
       if (e.code !== "MODULE_NOT_FOUND") { throw e; }
-      abort("Can't load module \"" + id + "\".");
+      abortError(`Can't load module "${id}".`, e);
     }
     return mod;
-  });
+  }));
   delete options.plugin;
 }
 
@@ -2409,19 +2454,23 @@ if (options.exportVar !== undefined) {
   }
 }
 
-let inputFile = null;
+let inputFile = options.input;
 switch (program.args.length) {
   case 0:
-    inputFile = "-";
+    inputFile = inputFile ? inputFile : "-";
     break;
 
   case 1:
+    if (inputFile) {
+      abort("Do not specify input both on command line and in config file.");
+    }
     inputFile = program.args[0];
     break;
 
   default:
     abort("Too many arguments.");
 }
+
 let outputFile = options.output;
 if (!outputFile) {
   outputFile = ((inputFile === "-") || options.test || options.testFile)
@@ -2448,14 +2497,13 @@ if (options.testFile) {
 }
 
 if (verbose) {
-  console.error("OPTIONS:", options);
-}
-// Files
-
-function readStream(inputStream, callback) {
-  let input = "";
-  inputStream.on("data", data => { input += data; });
-  inputStream.on("end", () => { callback(input); });
+  console.error("OPTIONS:", util__default['default'].inspect(options, {
+    depth: Infinity,
+    colors: process.stdout.isTTY,
+  }));
+  console.error("INPUT:", inputFile);
+  console.error("OUTPUT:", outputFile);
+  console.error("TEST TEXT:", testText);
 }
 
 // Main
@@ -2480,18 +2528,7 @@ readStream(inputStream, input => {
   try {
     source = peg__default['default'].generate(input, options);
   } catch (e) {
-    if (typeof e.format === "function") {
-      abort(e.format([{
-        source: options.grammarSource,
-        text: input,
-      }]));
-    } else {
-      if (verbose) {
-        abort(e);
-      } else {
-        abort(`Error: ${e.message}`);
-      }
-    }
+    abortError("Error parsing grammar:", e);
   }
 
   if (testText) {
@@ -2500,18 +2537,7 @@ readStream(inputStream, input => {
         grammarSource: testGrammarSource,
       });
     } catch (e) {
-      if (typeof e.format === "function") {
-        abort(e.format([{
-          source: testGrammarSource,
-          text: testText,
-        }]));
-      } else {
-        if (verbose) {
-          abort(e);
-        } else {
-          abort(`Error: ${e.message}`);
-        }
-      }
+      abortError("Error parsing test:", e);
     }
     source = util__default['default'].inspect(source, {
       depth: Infinity,
diff --git a/bin/peggy.mjs b/bin/peggy.mjs
index 4e91af67..4edf82fb 100644
--- a/bin/peggy.mjs
+++ b/bin/peggy.mjs
@@ -6,6 +6,8 @@ import util from "util";
 
 const MODULE_FORMATS = ["amd", "commonjs", "es", "globals", "umd"];
 const MODULE_FORMATS_WITH_DEPS = ["amd", "commonjs", "es", "umd"];
+const DEFAULT_FORMAT = "COMMON_JS";
+let verbose = false;
 
 // Helpers
 
@@ -14,6 +16,22 @@ function abort(message) {
   process.exit(1);
 }
 
+function abortError(msg, error) {
+  console.error(msg);
+  if (typeof error.format === "function") {
+    abort(error.format([{
+      source: testGrammarSource,
+      text: testText,
+    }]));
+  } else {
+    if (verbose) {
+      abort(error);
+    } else {
+      abort(`Error: ${error.message}`);
+    }
+  }
+}
+
 function addExtraOptions(options, json) {
   let extraOptions;
 
@@ -22,7 +40,7 @@ function addExtraOptions(options, json) {
   } catch (e) {
     if (!(e instanceof SyntaxError)) { throw e; }
 
-    abort("Error parsing JSON: " + e.message);
+    abortError("Error parsing JSON:", e);
   }
   if ((extraOptions === null)
       || (typeof extraOptions !== "object")
@@ -32,12 +50,20 @@ function addExtraOptions(options, json) {
   return Object.assign({}, options, extraOptions);
 }
 
+// Files
+
+function readStream(inputStream, callback) {
+  let input = "";
+  inputStream.on("data", data => { input += data; });
+  inputStream.on("end", () => { callback(input); });
+}
+
 function readFile(name) {
   let f = null;
   try {
     f = fs.readFileSync(name, "utf8");
   } catch (e) {
-    abort(`Can't read from file "${name}".`);
+    abortError(`Can't read from file "${name}".`, e);
   }
   return f;
 }
@@ -45,7 +71,7 @@ function readFile(name) {
 // Command line processing
 
 const program = new Command();
-const options = program
+let options = program
   .version(peg.VERSION, "-v, --version")
   .arguments("[input_file]")
   .addOption(
@@ -75,9 +101,15 @@ const options = program
     (val, prev) => addExtraOptions(prev, val)
   )
   .option(
-    "--extra-options-file <file>",
-    "file with additional options (in JSON format as an object) to pass to peg.generate",
-    (val, prev) => addExtraOptions(prev, readFile(val))
+    "-c, --extra-options-file <file>",
+    "file with additional options (in JSON or commonjs module format as an object) to pass to peg.generate",
+    (val, prev) => {
+      if (/\.c?js$/.test(val)) {
+        return Object.assign({}, prev, require(path.resolve(val)));
+      } else {
+        return addExtraOptions(prev, readFile(val));
+      }
+    }
   )
   .addOption(
     new Option(
@@ -85,7 +117,7 @@ const options = program
       "format of the generated parser"
     )
       .choices(MODULE_FORMATS)
-      .default("commonjs")
+      .default(DEFAULT_FORMAT, '"commonjs"')
   )
   .option("-o, --output <file>", "output file")
   .option(
@@ -111,7 +143,6 @@ const options = program
   .addOption(
     new Option("-O, --optimize <style>")
       .hideHelp()
-      .default("speed")
       .argParser(() => {
         console.error("Option --optimize is deprecated from 1.2.0 and has no effect anymore.");
         console.error("It will be deleted in 2.0.");
@@ -126,22 +157,36 @@ if (options.extraOptions) {
   Object.assign(options, options.extraOptions);
   delete options.extraOptions;
 }
-if (options.extraOptionsFile) {
-  Object.assign(options, options.extraOptionsFile);
-  delete options.extraOptionsFile;
-}
-
-const verbose = options.verbose;
-delete options.verbose;
 
+// Ensure defaults do not clobber config file
 if (options.allowedStartRules.length === 0) {
   // [] is an invalid input, as is null
   // undefined doesn't work as a default in commander
   delete options.allowedStartRules;
 }
 
+if (options.extraOptionsFile) {
+  // Ensure defaults do not clobber config file
+  const fmt = options.format;
+  delete options.format;
+
+  // Command line overwrites config file
+  options = Object.assign({}, options.extraOptionsFile, options);
+  delete options.extraOptionsFile;
+
+  if (fmt !== DEFAULT_FORMAT) {
+    options.format = fmt;
+  }
+}
+if (!options.format || (options.format === DEFAULT_FORMAT)) {
+  options.format = "commonjs";
+}
+
+verbose = Boolean(options.verbose);
+delete options.verbose;
+
 if (options.plugin) {
-  options.plugins = options.plugin.map(val => {
+  options.plugins = (options.plugins || []).concat(options.plugin.map(val => {
     // If this is an absolute or relative path (not a module name)
     const id = (path.isAbsolute(val) || /^\.\.?[/\\]/.test(val))
       ? path.resolve(val)
@@ -151,10 +196,10 @@ if (options.plugin) {
       mod = require(id);
     } catch (e) {
       if (e.code !== "MODULE_NOT_FOUND") { throw e; }
-      abort("Can't load module \"" + id + "\".");
+      abortError(`Can't load module "${id}".`, e);
     }
     return mod;
-  });
+  }));
   delete options.plugin;
 }
 
@@ -178,19 +223,23 @@ if (options.exportVar !== undefined) {
   }
 }
 
-let inputFile = null;
+let inputFile = options.input;
 switch (program.args.length) {
   case 0:
-    inputFile = "-";
+    inputFile = inputFile ? inputFile : "-";
     break;
 
   case 1:
+    if (inputFile) {
+      abort("Do not specify input both on command line and in config file.");
+    }
     inputFile = program.args[0];
     break;
 
   default:
     abort("Too many arguments.");
 }
+
 let outputFile = options.output;
 if (!outputFile) {
   outputFile = ((inputFile === "-") || options.test || options.testFile)
@@ -217,14 +266,13 @@ if (options.testFile) {
 }
 
 if (verbose) {
-  console.error("OPTIONS:", options);
-}
-// Files
-
-function readStream(inputStream, callback) {
-  let input = "";
-  inputStream.on("data", data => { input += data; });
-  inputStream.on("end", () => { callback(input); });
+  console.error("OPTIONS:", util.inspect(options, {
+    depth: Infinity,
+    colors: process.stdout.isTTY,
+  }));
+  console.error("INPUT:", inputFile);
+  console.error("OUTPUT:", outputFile);
+  console.error("TEST TEXT:", testText);
 }
 
 // Main
@@ -249,18 +297,7 @@ readStream(inputStream, input => {
   try {
     source = peg.generate(input, options);
   } catch (e) {
-    if (typeof e.format === "function") {
-      abort(e.format([{
-        source: options.grammarSource,
-        text: input,
-      }]));
-    } else {
-      if (verbose) {
-        abort(e);
-      } else {
-        abort(`Error: ${e.message}`);
-      }
-    }
+    abortError("Error parsing grammar:", e);
   }
 
   if (testText) {
@@ -269,18 +306,7 @@ readStream(inputStream, input => {
         grammarSource: testGrammarSource,
       });
     } catch (e) {
-      if (typeof e.format === "function") {
-        abort(e.format([{
-          source: testGrammarSource,
-          text: testText,
-        }]));
-      } else {
-        if (verbose) {
-          abort(e);
-        } else {
-          abort(`Error: ${e.message}`);
-        }
-      }
+      abortError("Error parsing test:", e);
     }
     source = util.inspect(source, {
       depth: Infinity,
diff --git a/docs/documentation.html b/docs/documentation.html
index f0f0bb18..bddd6b32 100644
--- a/docs/documentation.html
+++ b/docs/documentation.html
@@ -193,6 +193,27 @@ <h3 id="generating-a-parser-command-line">Command Line</h3>
 
 </dl>
 
+<p>
+If you specify options using `-c <file>` or `--extra-options-file <file>`, you
+will need to ensure you are using the correct types.  In particular, you may
+specify "plugin" as a string, or "plugins" as an array of objects that have a
+`use` method.  Always use the long (two-dash) form of the option.  Options
+that contain dashes should be specified in camel case. You may also specify an
+"input" field instead of using the command line.  For example:
+</p>
+
+<pre><code class="language-javascript">// config.js or config.cjs
+module.exports = {
+  allowedStartRules = ["foo", "bar"],
+  format: "umd",
+  exportVar: "foo",
+  input: "fooGrammar.peggy",
+  plugins: [require("./plugin.js")],
+  testFile: "myTestInput.foo",
+  trace: true
+};
+</code></pre>
+
 <h3 id="generating-a-parser-javascript-api">JavaScript API</h3>
 
 <p>In Node.js, require the Peggy parser generator module:</p>
diff --git a/test/cli/fixtures/options.js b/test/cli/fixtures/options.js
new file mode 100644
index 00000000..3b236f65
--- /dev/null
+++ b/test/cli/fixtures/options.js
@@ -0,0 +1,8 @@
+"use strict";
+
+module.exports = {
+  plugins: [require("./plugin.js")],
+  cli_test: {
+    words: ["zazzy"],
+  },
+};
diff --git a/test/cli/fixtures/options.json b/test/cli/fixtures/options.json
index 3c1433d5..2a4aa17b 100644
--- a/test/cli/fixtures/options.json
+++ b/test/cli/fixtures/options.json
@@ -1,3 +1,5 @@
 {
-  "allowedStartRules": ["foo", "bar", "baz"]
+  "allowedStartRules": ["foo", "bar", "baz"],
+  "format": "umd",
+  "input": "-"
 }
diff --git a/test/cli/run.spec.ts b/test/cli/run.spec.ts
index bca7ffdc..102705e8 100644
--- a/test/cli/run.spec.ts
+++ b/test/cli/run.spec.ts
@@ -78,34 +78,35 @@ describe("Command Line Interface", () => {
 Usage: peggy [options] [input_file]
 
 Options:
-  -v, --version                  output the version number
-  --allowed-start-rules <rules>  comma-separated list of rules the generated
-                                 parser will be allowed to start parsing from
-                                 (default: the first rule in the grammar)
-  --cache                        make generated parser cache results
-  -d, --dependency <dependency>  use specified dependency (can be specified
-                                 multiple times)
-  -e, --export-var <variable>    name of a global variable into which the
-                                 parser object is assigned to when no module
-                                 loader is detected
-  --extra-options <options>      additional options (in JSON format as an
-                                 object) to pass to peg.generate
-  --extra-options-file <file>    file with additional options (in JSON format
-                                 as an object) to pass to peg.generate
-  --format <format>              format of the generated parser (choices:
-                                 "amd", "commonjs", "es", "globals", "umd",
-                                 default: "commonjs")
-  -o, --output <file>            output file
-  --plugin <module>              use a specified plugin (can be specified
-                                 multiple times)
-  -t, --test <text>              Test the parser with the given text,
-                                 outputting the result of running the parser
-                                 instead of the parser itself
-  -T, --test-file <filename>     Test the parser with the contents of the given
-                                 file, outputting the result of running the
-                                 parser instead of the parser itself
-  --trace                        enable tracing in generated parser
-  -h, --help                     display help for command
+  -v, --version                    output the version number
+  --allowed-start-rules <rules>    comma-separated list of rules the generated
+                                   parser will be allowed to start parsing from
+                                   (default: the first rule in the grammar)
+  --cache                          make generated parser cache results
+  -d, --dependency <dependency>    use specified dependency (can be specified
+                                   multiple times)
+  -e, --export-var <variable>      name of a global variable into which the
+                                   parser object is assigned to when no module
+                                   loader is detected
+  --extra-options <options>        additional options (in JSON format as an
+                                   object) to pass to peg.generate
+  -c, --extra-options-file <file>  file with additional options (in JSON or
+                                   commonjs module format as an object) to pass
+                                   to peg.generate
+  --format <format>                format of the generated parser (choices:
+                                   "amd", "commonjs", "es", "globals", "umd",
+                                   default: "commonjs")
+  -o, --output <file>              output file
+  --plugin <module>                use a specified plugin (can be specified
+                                   multiple times)
+  -t, --test <text>                Test the parser with the given text,
+                                   outputting the result of running the parser
+                                   instead of the parser itself
+  -T, --test-file <filename>       Test the parser with the contents of the
+                                   given file, outputting the result of running
+                                   the parser instead of the parser itself
+  --trace                          enable tracing in generated parser
+  -h, --help                       display help for command
 `;
 
     expect(await exec({
@@ -214,12 +215,32 @@ baz = "3"
 
   it("handles extra options in a file", async() => {
     const optFile = path.join(__dirname, "fixtures", "options.json");
-    await expect(exec({
+    const optFileJS = path.join(__dirname, "fixtures", "options.js");
+
+    const res = await exec({
       args: ["--extra-options-file", optFile],
       stdin: "foo = '1'",
-    })).resolves.toMatch(
+    });
+    expect(res).toMatch(
       /startRuleFunctions = { foo: [^, ]+, bar: [^, ]+, baz: \S+ }/
     );
+    expect(res).toMatch("(function(root, factory) {");
+
+    // Intentional overwrite
+    await expect(exec({
+      args: ["-c", optFile, "--format", "amd"],
+      stdin: "foo = '1'",
+    })).resolves.toMatch(/^define\(/m);
+
+    await expect(exec({
+      args: ["-c", optFileJS],
+      stdin: "foo = zazzy:'1'",
+    })).rejects.toThrow("Error: Label can't be a reserved word \"zazzy\"");
+
+    await expect(exec({
+      args: ["-c", optFile, "____ERROR____FILE_DOES_NOT_EXIST"],
+      stdin: "foo = '1'",
+    })).rejects.toThrow("Do not specify input both on command line and in config file.");
 
     await expect(exec({
       args: ["--extra-options-file"],
@@ -342,8 +363,8 @@ baz = "3"
     })).resolves.toMatch("name: 'peggy'"); // Output is JS, not JSON
 
     await expect(exec({
-      args: ["-T", "__DIRECTORY__/__DOES/NOT__/__EXIST__/none.js", grammarFile],
-    })).rejects.toThrow("Can't read from file \"__DIRECTORY__/__DOES/NOT__/__EXIST__/none.js\".");
+      args: ["-T", "____ERROR____FILE_DOES_NOT_EXIST.js", grammarFile],
+    })).rejects.toThrow("Can't read from file \"____ERROR____FILE_DOES_NOT_EXIST.js\".");
 
     await expect(exec({
       args: ["-t", "boo", "-T", "foo"],