diff --git a/calendar/inc/class.calendar_bo.inc.php b/calendar/inc/class.calendar_bo.inc.php
index 609c69166a..cd63ca2b2d 100644
--- a/calendar/inc/class.calendar_bo.inc.php
+++ b/calendar/inc/class.calendar_bo.inc.php
@@ -348,6 +348,7 @@ class calendar_bo
 
 		// Email list
 		$contacts_obj = new Api\Contacts();
+		$bo = new calendar_bo();
 		foreach($ids as $id)
 		{
 			$list = $contacts_obj->read_list((int)$id);
@@ -356,6 +357,7 @@ class calendar_bo
 				'res_id' => $id,
 				'rights' => self::ACL_READ_FOR_PARTICIPANTS,
 				'name' => $list['list_name'],
+				'resources' => $bo->enum_mailing_list('l'.$id, false, false)
 			);
 		}
 
@@ -465,6 +467,22 @@ class calendar_bo
 			{
 				if ($user && !in_array($user,$users))	// already added?
 				{
+					// General expansion check
+					if (!is_numeric($user) && $this->resources[$user[0]]['info'])
+					{
+						$info = $this->resource_info($user);
+						if($info && $info['resources'])
+						{
+							foreach($info['resources'] as $_user)
+							{
+								if($_user && !in_array($_user, $users))
+								{
+									$users[] = $_user;
+								}
+							}
+							continue;
+						}
+					}
 					$users[] = $user;
 				}
 			}
diff --git a/calendar/inc/class.calendar_owner_etemplate_widget.inc.php b/calendar/inc/class.calendar_owner_etemplate_widget.inc.php
index 8ce445808c..c6d234f79f 100644
--- a/calendar/inc/class.calendar_owner_etemplate_widget.inc.php
+++ b/calendar/inc/class.calendar_owner_etemplate_widget.inc.php
@@ -78,9 +78,14 @@ class calendar_owner_etemplate_widget extends Etemplate\Widget\Taglist
 		foreach($value as &$owner)
 		{
 			$label = self::get_owner_label($owner);
+			$info = array();
 			if(!is_numeric($owner))
 			{
 				$resource = $bo->resources[substr($owner, 0,1)];
+				if($resource['info'])
+				{
+					$info = $bo->resource_info($owner);
+				}
 			}
 			else if (!in_array($owner, array_keys($accounts)))
 			{
@@ -90,7 +95,7 @@ class calendar_owner_etemplate_widget extends Etemplate\Widget\Taglist
 			{
 				continue;
 			}
-			$sel_options[] = array('value' => $owner, 'label' => $label, 'app' => lang($resource['app']));
+			$sel_options[] = array('value' => $owner, 'label' => $label, 'app' => lang($resource['app'])) + $info;
 		}
 	}
 
@@ -135,6 +140,7 @@ class calendar_owner_etemplate_widget extends Etemplate\Widget\Taglist
 
 		$bo = new calendar_bo();
 		$query = $_REQUEST['query'];
+		
 		// Arbitrarily limited to 50 / resource
 		$options = array('start' => 0, 'num_rows' => 50) +
 			array_diff_key($_REQUEST, array_flip(array('menuaction','query')));
@@ -156,6 +162,10 @@ class calendar_owner_etemplate_widget extends Etemplate\Widget\Taglist
 					$_results = array_intersect_key($_results, $GLOBALS['egw']->acl->get_grants('calendar'));
 				}
 			}
+			else if ($data['app'] && $data['search'])
+			{
+				$_results = call_user_func_array($data['search'], array($query, $options));
+			}
 			else if ($data['app'] && Link::get_registry($data['app'], 'query'))
 			{
 				$_results = Link::query($data['app'], $query,$options);
diff --git a/calendar/js/et2_widget_event.js b/calendar/js/et2_widget_event.js
index 28773edf44..8a3e17e9f2 100644
--- a/calendar/js/et2_widget_event.js
+++ b/calendar/js/et2_widget_event.js
@@ -918,18 +918,36 @@ et2_calendar_event.owner_check = function owner_check(event, parent, owner_too)
 	{
 		owner_too = app.calendar.state.status_filter === 'owner';
 	}
+	var options = false
+	if(app.calendar && app.calendar.sidebox_et2 && app.calendar.sidebox_et2.getWidgetById('owner'))
+	{
+		options = app.calendar.sidebox_et2.getWidgetById('owner').taglist.getSelection();
+	}
+	else
+	{
+		options = this.getArrayMgr("sel_options").getRoot().getEntry('owner');
+	}
 	if(event.participants && parent.options.owner)
 	{
-		var parent_owner = typeof parent.options.owner !== 'object' ?
+		var parent_owner = jQuery.extend([], typeof parent.options.owner !== 'object' ?
 			[parent.options.owner] :
-			parent.options.owner;
+			parent.options.owner);
 		owner_match = false;
 		var length = parent_owner.length;
 		for(var i = 0; i < length; i++ )
 		{
-			// Exception for mailing lists, they won't match and we don't have the
-			// list client side.
-			if(parent_owner[i][0] === 'l') return true;
+			// Handle grouped resources like mailing lists, they won't match so
+			// we need the list - pull it from sidebox owner
+			if(isNaN(parent_owner[i]) && options && options.find)
+			{
+				var resource = options.find(function(element) {return element.id == parent_owner[i];}) || {};
+				if(resource && resource.resources)
+				{
+					parent_owner.splice(i,1);
+					parent_owner = parent_owner.concat(resource.resources);
+					continue;
+				}
+			}
 			
 			if (parseInt(parent_owner[i]) < 0)
 			{
diff --git a/resources/inc/class.resources_bo.inc.php b/resources/inc/class.resources_bo.inc.php
index 83169666f8..08b47bd725 100755
--- a/resources/inc/class.resources_bo.inc.php
+++ b/resources/inc/class.resources_bo.inc.php
@@ -519,21 +519,113 @@ class resources_bo
 		return $acc_list;
 	}
 
+	/**
+	 * Search for resources for calendar to select as participants
+	 * 
+	 * Search and options match Link::query()
+	 * 
+	 * Resources return actual resources as well as categories that match
+	 * 
+	 * @param String $search - Search string
+	 * @param Array $options - search options
+	 * @see Link::query()
+	 * 
+	 * @return Array List of ID => Title entries matching search string
+	 */
+	public static function calendar_search($search, $options)
+	{
+		// Resources
+		$list = Link::query('resources', $search, $options);
+
+		// Categories
+		$bo = new resources_bo();
+		$cats = $bo->acl->get_cats(Acl::READ);
+		foreach($cats as $cat_id => $cat)
+		{
+			if($cat && stripos($cat, $search) !== FALSE)
+			{
+				// Get resources for that category
+				$resources = $bo->get_resources_by_category($cat_id);
+
+				// Edit dialog sends exec as an option, don't add categories
+				if(count($resources) && !$options['exec'])
+				{
+					$list['cat-'.$cat_id] = array(
+						'label'	=>	$cat,
+						'resources'	=>	$resources,
+					);
+				}
+				else if ($resources && $options['exec'])
+				{
+					array_map(
+						function($id,$name) use (&$list) { $list[''+$id] = $name;},
+						array_keys($resources), $resources
+					);
+				}
+			}
+		}
+
+		return $list;
+	}
+
+	/**
+	 * Get a list of resources (ID => name) matching a single category ID
+	 * @param int $cat_id
+	 * @return array()
+	 */
+	public function get_resources_by_category($cat_id)
+	{
+		$resources = array();
+		$filter = array(
+			'cat_id' => $cat_id,
+			//'accessory_of' => '-1'
+			'deleted' => null
+		);
+		$only_keys = 'res_id,name';
+		$data = $this->so->search(array(),$only_keys,$order_by='name',$extra_cols='',$wildcard='%',$empty,$op='OR',$limit,$filter);
+		foreach($data as $resource)
+		{
+			$resources[$resource['res_id']] = $resource['name'];
+		}
+
+		return $resources;
+	}
+
 	/**
 	 * returns info about resource for calender
 	 * @author Cornelius Weiss<egw@von-und-zu-weiss.de>
-	 * @param int|array $res_id single id or array $num => $res_id
+	 * @param int|array|string $res_id single id, array $num => $res_id or
+	 *	'cat-<cat_id>' for the whole category
 	 * @return array
 	 */
 	function get_calendar_info($res_id)
 	{
-		//echo "<p>resources_bo::get_calendar_info(".print_r($res_id,true).")</p>\n";
+		//error_log(__METHOD__ . "(".print_r($res_id,true).")");
+
+		// Resource category
+		if(is_string($res_id) && strpos($res_id, 'cat-') === 0)
+		{
+			$cat_id = (int)substr($res_id, 4);
+			if(!$this->acl->is_permitted($cat_id, Acl::READ))
+			{
+				return array();
+			}
+			return array( array(
+				'name' => $this->acl->get_cat_name($cat_id),
+				'rights' => $this->acl->get_permissions($cat_id),
+				'resources' => array_map(
+					function($id) { return 'r'.$id;},
+					array_keys($this->get_resources_by_category($cat_id))
+				)
+			));
+		}
+		
 		if(!is_array($res_id) && $res_id < 1) return;
 
 		$data = $this->so->search(array('res_id' => $res_id),self::TITLE_COLS.',useable');
 		if (!is_array($data))
 		{
-			error_log(__METHOD__." No Calendar Data found for Resource with id $res_id");
+			//error_log(__METHOD__." No Calendar Data found for Resource with id $res_id");
 			return array();
 		}
 		foreach($data as $num => &$resource)
@@ -611,10 +703,11 @@ class resources_bo
 		{
 			$filter['accessory_of'] = $options['accessory_of'];
 		}
+		$list = array();
 		$data = $this->so->search($criteria,$only_keys,$order_by='name',$extra_cols='',$wildcard='%',$empty,$op='OR',$limit,$filter);
 		// maybe we need to check disponibility of the searched resources in the calendar if $pattern ['exec'] contains some extra args
 		$show_conflict=False;
-		if ($options['exec'] && $GLOBALS['egw_info']['preferences']['calendar']['defaultresource_sel'] !== 'resources')
+		if ($data && $options['exec'] && $GLOBALS['egw_info']['preferences']['calendar']['defaultresource_sel'] !== 'resources')
 		{
 			// we'll use a cache for resources info taken from database
 			static $res_info_cache = array();
diff --git a/resources/inc/class.resources_hooks.inc.php b/resources/inc/class.resources_hooks.inc.php
index 57f41d360d..3eb73def35 100644
--- a/resources/inc/class.resources_hooks.inc.php
+++ b/resources/inc/class.resources_hooks.inc.php
@@ -101,7 +101,7 @@ class resources_hooks
 	function calendar_resources($args)
 	{
 		return array(
-			'widget' => 'resources_select',// widget to use for the selection of resources
+			'search' => 'resources_bo::calendar_search',// method to use for the selection of resources, otherwise Link system is used
 			'info' => 'resources.resources_bo.get_calendar_info',// info method, returns array with id, type & name for a given id
 			'max_quantity' => 'useable',// if set, key for max. quantity in array returned by info method
 			'new_status' => 'resources.resources_bo.get_calendar_new_status',// method returning the status for new items, else 'U' is used