Colorado 74, Oregon State 68: Spencer Dinwiddie scored 20 points as the fifth-seeded Buffaloes held on to win the Pac-12 tournament first-round game in Las Vegas.

Xavier Johnson had 16 points and eight rebounds and Andre Roberson had 12 points and seven rebounds for Colorado (21-10), which will play fourth-seeded Arizona in Thursday’s quarterfinals.

Roberto Nelson scored 20 points, Eric Moreland had 14 points, 13 rebounds and five blocks and Devon Collier scored 13 for No. 12 seed Oregon State (14-18).

Colorado collected eight of its 15 offensive rebounds in the first half while building a 32-26 lead. The Buffaloes closed the first half on a 7-0 run, capped by Dinwiddie’s half-court 3-pointer with one second left.

Roberson and fellow front-court starter Josh Scott picked up their third fouls during the first three minutes of the second half, but the Buffaloes continued to press on. Dinwiddie sank another 3-pointer and made three consecutive free throws on the next trip down the floor, extending Colorado’s lead back to seven with 12:38 left and the Beavers never got back within four.

GAME NOTEBOOK: Roberson, the Pac-12 Defensive Player of the Year who averaged a nation-leading 11.5 rebounds and conference-best 2.3 steals during the regular season, was doubtful earlier in the week after missing the last two games and Monday's practice with mononucleosis. … Colorado is 9-1 on neutral courts dating back to last season’s run to the Pac-12 tournament championship. … The Buffaloes held their 11th consecutive conference opponent to fewer than 70 points, the program’s longest streak since 1962.