I think he voiced a whole episode. Watch this part first.
Then the show here.
http://www.hulu.com/watch/181123/family-guy-excellence-in-broadcasting
Great episode! And yes, it was Rush 100%. He’s in this video talking with Seth about being in the episode:
Rainn Wilson also did his own voice on the short part where they were watching The Office.
Rush let them take a few blows at him. He does have a sense of humor.