Dwayne Benjamin added 25 points for Oregon (17-7, 7-4 Pac-12), which raced to a 52-28 halftime lead on the way to its fifth win in its last six games.
Dexter Kernick-Drew led the Cougars (10-13, 4-7) with 18 points off the bench. Shorewood High School product Josh Hawkinson added 14 and former Curtis High School star DaVonte Lacy had 13.
Oregon’s lead ballooned to a high of 32 on the strength of 11 points by Benjamin in the first 3 ½ minutes of the second half.
The victory avenged the Ducks’ 108-99 overtime loss to Washington State in Pullman last month.
It also ruined the homecoming for WSU coach Ernie Kent, who was coaching for the first time against Oregon after being fired in 2010 after 13 seasons.
Oregon leading rebounder Jordan Bell served his one-game suspension due an incident that took place on campus earlier this week.