Buffalo led 49-48 with 7:02 left before the Cougars used a 13-1 run to pull away. The Bulls went nearly six minutes without a field goal during Washington State's run.
Lacy tied his career high with five 3-pointers for Washington State (8-4), which has won three straight and six of seven. Motum had eight of his 15 points in the second half for the Cougars and Dexter Kernich-Drew added 10.
Motum had two put-backs to ignite the run, including one after a missed free throw. Kernich-Drew hit a 3-pointer to make it 56-50 with 4:53 remaining in the game.