O’Neil became the first black coach ever hired by a major league team when he was signed by the Cubs in 1962. From 1948 through 1955, he managed some of the finest Kansas City Monarch clubs, leading them to five pennants and two Black World Series. He managed East-West all-star teams in 1951-54. Among his players were more than 20 future major leaguers, including Ernie Banks, Elston Howard, and Hank Thompson. O’Neil had been an excellent clutch hitter and a top first baseman. He led the Negro National League with a .353 batting average in 1946, then hit .333 with two home runs in the BWS. O’Neil was the first officially recognized black coach ever hired by a major league team.