diff --git a/common/changes/@uifabric/utilities/mapol-allow-settings-to-merge_2018-04-25-18-45.json b/common/changes/@uifabric/utilities/mapol-allow-settings-to-merge_2018-04-25-18-45.json
new file mode 100644
index 00000000000000..5c308b374c1a41
--- /dev/null
+++ b/common/changes/@uifabric/utilities/mapol-allow-settings-to-merge_2018-04-25-18-45.json
@@ -0,0 +1,11 @@
+{
+  "changes": [
+    {
+      "packageName": "@uifabric/utilities",
+      "comment": "Allow a function to be passed to the Customizers props",
+      "type": "minor"
+    }
+  ],
+  "packageName": "@uifabric/utilities",
+  "email": "mark@thedutchies.com"
+}
\ No newline at end of file
diff --git a/packages/utilities/src/Customizations.ts b/packages/utilities/src/Customizations.ts
index ecf0cae86a9ff2..a60a282a5d8548 100644
--- a/packages/utilities/src/Customizations.ts
+++ b/packages/utilities/src/Customizations.ts
@@ -5,11 +5,13 @@ import {
   EventGroup
 } from './EventGroup';
 
+// tslint:disable-next-line:no-any
+export type Settings = { [key: string]: any };
+export type SettingsFunction = (settings: Settings) => Settings;
+
 export interface ICustomizations {
-  // tslint:disable-next-line:no-any
-  settings: { [key: string]: any };
-  // tslint:disable-next-line:no-any
-  scopedSettings: { [key: string]: { [key: string]: any } };
+  settings: Settings;
+  scopedSettings: { [key: string]: Settings };
 }
 
 const CustomizationsGlobalKey = 'customizations';
@@ -29,13 +31,13 @@ export class Customizations {
   }
 
   // tslint:disable-next-line:no-any
-  public static applySettings(settings: { [key: string]: any }): void {
+  public static applySettings(settings: Settings): void {
     _allSettings.settings = { ..._allSettings.settings, ...settings };
     Customizations._raiseChange();
   }
 
   // tslint:disable-next-line:no-any
-  public static applyScopedSettings(scopeName: string, settings: { [key: string]: any }): void {
+  public static applyScopedSettings(scopeName: string, settings: Settings): void {
     _allSettings.scopedSettings[scopeName] = { ..._allSettings.scopedSettings[scopeName], ...settings };
     Customizations._raiseChange();
   }
@@ -47,7 +49,7 @@ export class Customizations {
     // tslint:disable-next-line:no-any
   ): any {
     // tslint:disable-next-line:no-any
-    const settings: { [key: string]: any } = {};
+    const settings: Settings = {};
     const localScopedSettings = (scopeName && localSettings.scopedSettings[scopeName]) || {};
     const globalScopedSettings = (scopeName && _allSettings.scopedSettings[scopeName]) || {};
 
diff --git a/packages/utilities/src/Customizer.test.tsx b/packages/utilities/src/Customizer.test.tsx
index cfb3004ce966c9..2e885dd50e6b3b 100644
--- a/packages/utilities/src/Customizer.test.tsx
+++ b/packages/utilities/src/Customizer.test.tsx
@@ -54,7 +54,7 @@ describe('Customizer', () => {
   });
 
   it('can scope settings to specific components', () => {
-    let scopedSettings = {
+    const scopedSettings = {
       Foo: { field: 'scopedToFoo' },
       Bar: { field: 'scopedToBar' }
     };
@@ -91,4 +91,78 @@ describe('Customizer', () => {
     )).toEqual('<div>fieldfield2field3</div>');
   });
 
+  it('can layer scoped settings with scopedSettingsFunction', () => {
+    Customizations.applySettings({ 'field3': 'field3' });
+
+    expect(ReactDOM.renderToStaticMarkup(
+      <Customizer scopedSettings={ { Bar: { field: 'field' } } }>
+        <Customizer
+          scopedSettings={
+            // tslint:disable-next-line:jsx-no-lambda
+            (scopedSettings: { Bar: { field2: string } }) => ({ Bar: { ...scopedSettings.Bar, field2: 'field2' } })
+          }
+        >
+          <Bar />
+        </Customizer >
+      </Customizer >
+    )).toEqual('<div>fieldfield2field3</div>');
+  });
+
+  it('it allows scopedSettings to be merged when a function is passed', () => {
+    expect(ReactDOM.renderToStaticMarkup(
+      <Customizer scopedSettings={ { Foo: { field: 'scopedToFoo' } } }>
+        <Customizer
+          scopedSettings={
+            // tslint:disable-next-line:jsx-no-lambda
+            (settings: { Foo: { field: string } }) => ({ ...settings, Bar: { field: 'scopedToBar' } })
+          }
+        >
+          <div>
+            <Foo />
+            <Bar />
+          </div>
+        </Customizer>
+      </Customizer>
+    )).toEqual('<div><div>scopedToFoo</div><div>scopedToBar</div></div>');
+  });
+
+  it('does not override previously set settings', () => {
+    expect(ReactDOM.renderToStaticMarkup(
+      <Customizer settings={ { field: 'field1' } }>
+        <Customizer settings={ { field: 'field2' } }>
+          <Bar />
+        </Customizer >
+      </Customizer >
+    )).toEqual('<div>field1</div>');
+  });
+
+  it('overrides the old settings when the parameter is ignored', () => {
+    expect(ReactDOM.renderToStaticMarkup(
+      <Customizer settings={ { field: 'field1' } }>
+        <Customizer
+          settings={
+            // tslint:disable-next-line:jsx-no-lambda
+            (settings: { field: string }) => ({ field: 'field2' })
+          }
+        >
+          <Bar />
+        </Customizer >
+      </Customizer >
+    )).toEqual('<div>field2</div>');
+  });
+
+  it('can use a function to merge settings', () => {
+    expect(ReactDOM.renderToStaticMarkup(
+      <Customizer settings={ { field: 'field1' } }>
+        <Customizer
+          settings={
+            // tslint:disable-next-line:jsx-no-lambda
+            (settings: { field: string }) => ({ field: settings.field + 'field2' })
+          }
+        >
+          <Bar />
+        </Customizer >
+      </Customizer >
+    )).toEqual('<div>field1field2</div>');
+  });
 });
diff --git a/packages/utilities/src/Customizer.tsx b/packages/utilities/src/Customizer.tsx
index 302818a1fbee83..a842973a986686 100644
--- a/packages/utilities/src/Customizer.tsx
+++ b/packages/utilities/src/Customizer.tsx
@@ -1,13 +1,55 @@
 import * as React from 'react';
 import * as PropTypes from 'prop-types';
 import { BaseComponent, IBaseProps } from './BaseComponent';
-import { ICustomizations } from './Customizations';
+import { ICustomizations, Settings, SettingsFunction } from './Customizations';
 
 export interface ICustomizerContext {
   customizations: ICustomizations;
 }
 
-export type ICustomizerProps = Partial<ICustomizations> & IBaseProps;
+export type ICustomizerProps = IBaseProps & Partial<{
+  /**
+   * @description
+   * Settings are used as general settings for the React tree below.
+   * Components can subscribe to receive the settings by using `customizable`.
+   *
+   * @example
+   * Settings can be represented by a plain object that contains the key value pairs.
+   * ```
+   *  <Customizer settings={{ color: 'red' }} />
+   * ```
+   * or a function that receives the current settings and returns the new ones
+   * ```
+   *  <Customizer settings={(currentSettings) => ({ ...currentSettings, color: 'red' })} />
+   * ```
+   */
+  settings: Settings | SettingsFunction;
+  /**
+   * @description
+   * Scoped settings are settings that are scoped to a specific scope. The
+   * scope is the name that is passed to the `customizable` function when the
+   * the component is customized.
+   *
+   * @example
+   * Scoped settings can be represented by a plain object that contains the key value pairs.
+   * ```
+   *  const myScopedSettings = {
+   *    Button: { color: 'red' };
+   *  };
+   *
+   *  <Customizer scopedSettings={myScopedSettings} />
+   * ```
+   * or a function that receives the current settings and returns the new ones
+   * ```
+   *  const myScopedSettings = {
+   *    Button: { color: 'red' };
+   *  };
+   *
+   *  <Customizer scopedSettings={(currentScopedSettings) => ({ ...currentScopedSettings, ...myScopedSettings })} />
+   * ```
+   */
+  scopedSettings: Settings | SettingsFunction
+}>;
 
 /**
  * The Customizer component allows for default props to be mixed into components which
@@ -16,8 +58,9 @@ export type ICustomizerProps = Partial<ICustomizations> & IBaseProps;
  * 1. render svg icons instead of the icon font within all buttons
  * 2. inject a custom theme object into a component
  *
- * Props are provided via the settings prop, which should be a json map which contains 1 or more
- * name/value pairs representing injectable props.
+ * Props are provided via the settings prop which should be one of the following:
+ * - A json map which contains 1 or more name/value pairs representing injectable props.
+ * - A function that receives the current settings and returns the new ones that apply to the scope
  *
  * @public
  */
@@ -25,8 +68,8 @@ export class Customizer extends BaseComponent<ICustomizerProps, ICustomizerConte
   public static contextTypes: {
     customizations: PropTypes.Requireable<{}>;
   } = {
-    customizations: PropTypes.object
-  };
+      customizations: PropTypes.object
+    };
 
   public static childContextTypes: {
     customizations: PropTypes.Requireable<{}>;
@@ -56,30 +99,49 @@ export class Customizer extends BaseComponent<ICustomizerProps, ICustomizerConte
     props: ICustomizerProps,
     context: ICustomizerContext
   ): ICustomizerContext {
-    let {
-      settings = {},
-      scopedSettings = {}
-    } = props;
-    let {
+    const {
       customizations = { settings: {}, scopedSettings: {} }
     } = context;
 
-    let newScopedSettings = { ...scopedSettings };
-
-    for (let name in customizations.scopedSettings) {
-      if (customizations.scopedSettings.hasOwnProperty(name)) {
-        newScopedSettings[name] = { ...scopedSettings[name], ...customizations.scopedSettings[name] };
-      }
-    }
-
     return {
       customizations: {
-        settings: {
-          ...settings,
-          ...customizations.settings
-        },
-        scopedSettings: newScopedSettings
+        settings: mergeSettings(customizations.settings, props.settings),
+        scopedSettings: mergeScopedSettings(customizations.scopedSettings, props.scopedSettings),
       }
     };
   }
 }
+
+function mergeSettings(oldSettings: Settings = {}, newSettings?: Settings | SettingsFunction): Settings {
+  const mergeSettingsWith = isSettingsFunction(newSettings) ? newSettings : settingsMergeWith(newSettings);
+
+  return mergeSettingsWith(oldSettings);
+}
+
+function mergeScopedSettings(oldSettings: Settings = {}, newSettings?: Settings | SettingsFunction): Settings {
+  const mergeSettingsWith = isSettingsFunction(newSettings) ? newSettings : scopedSettingsMergeWith(newSettings);
+
+  return mergeSettingsWith(oldSettings);
+}
+
+function isSettingsFunction(settings?: Settings | SettingsFunction): settings is SettingsFunction {
+  return typeof settings === 'function';
+}
+
+function settingsMergeWith(newSettings?: object): (settings: Settings) => Settings {
+  return (settings: Settings) => newSettings ? { ...newSettings, ...settings } : settings;
+}
+
+function scopedSettingsMergeWith(scopedSettingsFromProps: Settings = {}): (scopedSettings: Settings) => Settings {
+  return (oldScopedSettings: Settings): Settings => {
+    const newScopedSettings: Settings = { ...oldScopedSettings };
+
+    for (let scopeName in scopedSettingsFromProps) {
+      if (scopedSettingsFromProps.hasOwnProperty(scopeName)) {
+        newScopedSettings[scopeName] = { ...oldScopedSettings[scopeName], ...scopedSettingsFromProps[scopeName] };
+      }
+    }
+
+    return newScopedSettings;
+  };
+}
\ No newline at end of file