Ocean's Three and a Half - S7-E7
Corrected entry: When Lois asks Brian where Peter is, he tells her that Peter, Joe, Quagmire and Cleveland went to rob her dad. There's no way Brian would have known this as he wasn't in the room when they were discussing the plan.
Correction: So much time passes that Brian had plenty of time and ways to find out. Peter could have even told Brian he's leaving to go rob his father-in-law since we don't see them leaving.
Bishop73