In 1947, O'Boyle was hired as head football coach and athletic director at Southwest Missouri State College. He led the Southwest Missouri State Bears football team for two seasons, compiling a record of 16–4–1 and winning the Missouri Intercollegiate Athletic Association title in 1948. O'Boyle worked as an assistant football coach at Kansas State University from 1949 to 1950, at Duke University from 1951 to 1958, and at the University of Miami from 1959 to 1960, before returning once more to his alma mater, in 1961. After one season as an assistant, he succeeded Andy Pilney as head football coach at Tulane. O'Boyle managed only a 6–33–1 record in four seasons before he quit his post at the end of the 1965 season, a campaign that ended with a 62–0 loss to the rival LSU Tigers (ironically, Pilney's tenure at Tulane ended in the exact same fashion four years earlier).[2]
The following year O'Boyle moved to the ranks of professional football, joining the Kansas City Chiefs of the American Football League (AFL) under head coach Hank Stram, with whom O'Boyle had worked as a fellow assistant at Miami. O'Boyle coached the Chiefs teams that appeared in the First AFL-NFL World Championship Game—later known as Super Bowl I—and won Super Bowl IV. He remained a coach with the team through their merger into the National Football League (NFL) until the end of the 1974 season. Thereafter, he worked as a scout with the Chiefs until his retirement in 1984.
