CORVALLIS, Ore - Mac Hopson's jumper with 35 seconds to go put Washington State ahead for good tonight as the ninth-ranked Cougars held off Oregon State, 58 to 54. Washington State was coming off a 64 to 59 loss to Number 23 Oregon on Thursday. That loss narrowed the Cougars' chances of catching U.C.L.A in the Pac-10 Conference race. The fourth-ranked Bruins clinched at least a share of the Pac-10 regular-season title by beating Stanford today. Washington State, which trailed by as many as eight points in the second half, pulled ahead when Aron Baynes scored eight straight points to give the Cougars a 47 to 45 lead. But the Beavers stayed in the game, and tied it at 54 before Hopson made his jumper, followed by a pair of free throws by Baynes for the final score. Baynes led the Cougars with 14 points. The Cougars will host U.C.L.A on Thursday, before closing out the regular season on Saturday against U.S.C.