In Boulder, Colo., Jim McMahon of Brigham Young passed for 263 yards and three touchdowns before leaving the game early in the third quarter with a knee injury.
McMahon, who completed 15 of 30 passes and added two NCAA records to the 35 he already had, suffered a hyper-extended left knee when hit by blitzing safety Ellis Wood with 13:41 left in the third quarter. The seriousness of the injury was not immediately known.
The senior quarterback threw scoring passes on the Cougars' first two possessions, a 44-yarder to split end Dan Plater and a seven-yarder to running back Scott Pettis. That give BYU a 14-0 lead with 7:34 left in the opening quarter.
Kurt Gunther kicked a 40-yard field goal in the second quarter, and McMahon boosted the lead to 24-0 with a three-yard scoring pass to freshman wide receiver Glen Kozlowski early in the second half.
Second-string quarterback Steve Young passed for two touchdowns in the second half as the Cougars raised their record to 4-0.
Colorado, stymied by turnovers and penalties, got three second-half scores. Randy Essington threw two touchdown passes and freshman halfback Lee Rouson scored on a seven-yard run. The loss dropped Colorado to 1-2.