Hello,

Try this,

<record model="ir.ui.menu" id="stock.menu_action_picking_tree">

<field name="groups_id" eval="[(4, ref('group_stock_manager_moseltex'))]"/>

</record>

you have to give reference of module associated with that menu. and menu_action_picking_tree belongs to stock module in odoo 7.0 Here 4 will add group to existing list of groups on that menu. If you want to replace existing groups on that menu than use 6 instead. example- (6,0,[ref('group_stock_manager_moseltex')].

There are six numeric commands:

• 0 - creates a new object and adds it to the Many2many relation
• 1 - updates an object that already exists on the relation
• 2 - deletes an object that already exists on the relation
• 3 - removes an existing object from the relation, without deleting it
• 4 - adds an existing object to the relation
• 5 - removes all objects from the relation, without deleting them
• 6 - replaces pervious objects existing on the relation with a new set of objects

Hope this will help you.