Josh Scott scored eight of his 19 points in overtime as No. 15 Colorado held off Washington State 71-70 on Wednesday night.
Askia Booker added 18 points for Colorado (14-2, 3-0 Pac-12), which has tied the second-best start in program history.
Dexter Kernich-Drew scored a career-high 24 points to lead Washington State (7-8, 0-3), which was playing without leading scorer DaVonte Lacy, who has a rib injury.
Colorado dominated the free throw shooting, making 26 of 38, while Washington State went to the line only three times, making them all.
Washington's Que Johnson hit a 3-pointer to send the game into overtime.
Scott made two baskets to push Colorado's lead to 66-60. After D.J. Shelton's 3-pointer pulled the Cougars to 70-67, Spencer Dinwiddie made a free throw for the Buffaloes and Washington State's Royce Woolridge hit a 3 for the final margin.