George Allen started coaching football at Morningside College and Whittier College, he entered the National Football League as offensive-end coach with the Los Angeles Rams. As an assistant coach of the Chicago Bears he coached the team's defensive unit in its 1963 league championship season. As head coach of the Los Angeles Rams from 1966 to 1970, he traded promising young talent to acquire experienced players, won two Western Division championships, and had the best win-loss-tie record in the league. His years of coaching the Washington Redskins were perhaps even more remarkable, for they included three consecutive Eastern Division championships, again after building his team around veteran players.
Allen went on to coach the Chicago Blitz and Arizona Wranglers in the short-lived United States Football League. In 1989 he returned to college football, coaching for a season at Long Beach State University. In 14 seasons as head coach of professional football teams Allen's record was 144-69-5.