http://social.msdn.microsoft.com/Forums/en-US/wpf/thread/c5b6a94b-2cdc-4cfb-8ccb-0f7e680586d7 If the ToolBars ItemsSource is DataBound, all buttons will appear in the overflow list until a manual window resize. This is an Workaround Control which invalidates it's Measure after Templates are applied.