Cox was promoted to coaching Tulane's linemen in 1929, and became the head coach before the 1932 season. He compiled a 28–10–2 record as head coach of the Green Wave. His 1934 team went 10–1, won a share of the Southeastern Conference championship, and defeated the Temple Owls in the Sugar Bowl.
Cox was promoted to coaching Tulane's offensive line in 1929, becoming head coach before the 1932 season. He led the Green Wave to a 28–10–2 record as head coach. His 1934 team went undefeated at 10-1, shared the Southeastern Conference championship, and defeated the Temple Owls in the Sugar Bowl.