Tolstoy's novel figures in at least three sitcom episodes:

1. MASH: Radar familiarizes himself with the book to impress an intellectual nurse;
2. Cheers: Sam reads War and Peace to impress Diane; and,
3. Seinfeld: Jerry tells Elaine the original title was "War, What Is It Good For?"

Are there other episodes it figures in?

Not exactly a sitcom episode, but in the special Happy New Year, Charlie Brown, Charlie Brown has to read it for a school assignment over the winter break.