Oklahoma coach Jeff Capel announced the players' departures on Wednesday, two weeks after the Sooners ended a 13-18 season, their first losing campaign since 1980-81.
Capel says Mason-Griffin plans to pursue a pro career. The 5-foot-11 point guard averaged 14.1 points and five assists per game this season as a freshman.
Willis, a 6-foot-6 sophomore, plans to transfer. He played in 13 games this season, averaging 2.6 points and 2.2 rebounds per game. As a freshman, he played in 16 games and averaged 3.3 points and 1.4 rebounds.
Capel says sophomore guard Willie Warren, who was the Sooners' leading scorer this past season, has not decided whether he will enter the NBA draft or return to Oklahoma.