On May 17, 1977 — The Chicago Cubs hit seven home runs in beating the San Diego Padres, 23 – 6, at Wrigley Field. Larry Biittner (two), Gene Clines, Steve Ontiveros, Dave Rosello, Jerry Morales and Bobby Murcer homer for the Cubs, with Biittner, Morales, and Murcer hitting consecutive shots in the 5th inning.
Source:
Baseball Reference May 17