Grocery.php

<?php

class Grocery extends DataObject {
	private static $db = array(
		'Name' => 'Varchar(255)',
		'Price' => 'Int'
	);

	private static $belongs_many_many = array(
		'GroceryPages' => 'GroceryPage'
	);
}

GroceryAdmin.php

<?php 

class GroceryAdmin extends ModelAdmin {
	private static $managed_models = array('Grocery');
	private static $url_segment = 'groceries';
	private static $menu_title = 'Groceries';
	private static $menu_icon = '/your/path/to/groceryicon.png';

}

GroceryPage.php

<?php

class GroceryPage extends Page {
	private static $many_many = array(
		'Groceries' => 'Grocery'
	);


	function getCMSFields() {
	    $fields = parent::getCMSFields();
 
	    $gridConfig = GridFieldConfig_RelationEditor::create();
	    $gridConfig->getComponentByType( 'GridFieldAddExistingAutocompleter' )->setSearchFields( array( 'Name' ) );
	    $gridConfig->getComponentByType( 'GridFieldPaginator' )->setItemsPerPage( 100 );
	    $gridField = new GridField( "Groceries", "List of Groceries:", $this->Groceries(), $gridConfig );
	    $fields->addFieldToTab( "Root.Groceries", $gridField );
	 
	    return $fields;
	}
}

class GroceryPage_Controller extends Page_Controller {

}