M'Baye came up with seven straight points for the Sooners (11-3, 2-0 Big 12) late in the second half to put the game away after their 14-point lead had been nearly eliminated.
Oklahoma went 8 for 13 from 3-point range and defended its home court in the Bedlam rivalry for the ninth straight season. The Cowboys (11-3, 1-2) haven't won in Norman since 2004, when they went on to win the Big 12 championship and reach the Final Four.
Seton Hall sophomore Isaiah Whitehead will stay in the NBA draft and not return for his junior season.
Washington State's trio of Josh Hawkinson, Conor Clifford and Ike Iroegbu have withdrawn from the NBA draft and will play their senior season with the Cougars.
Gonzaga center Przemek Karnowski, who missed most of last season with a back injury, says he is returning for another year.