He was hired as the head baseball coach and an assistant under head football coach Lloyd Helgeson. Sonoma State played football at the junior varsity level in 1969. Peterson succeeded Helgeson as head coach in 1970 when Sonoma State moved up to varsity status, competing at the NCAA College Division level. He led Sonoma State to a record of 6-12-1 over two seasons, 1970 and 1971 before the school disbanded its football program in 1972. Peterson left Sonoma State in February 1973.

In 1969,