Langston Morris-Walker scored 17 points and Gary Payton II had 11 points, eight rebounds, six steals and four assists to lead Oregon State (16-9, 7-6). Malcolm Duvivier and Daniel Gomis added 10 points apiece.
But the Beavers dropped to 2-9 away from home this season.
"We've got what we got," the Associate Press described a terse OSU coach Wayne Tinkle as saying. "We've just got to rest up, get home and get ready for the next one."
Oregon State led at the half, but momentum swung USC's way after that.
USC opened the second half on a 15-3 run to take its first lead since the game's opening minutes.
USC never let Oregon State get within two possessions the rest of the game. The Trojans finished it out with Elijah Stewart throwing up a layup on the fastbreak off the backboard into the waiting hands of Julian Jacobs, who threw down another emphatic slam to bring the crowd to its feet.
Pac-12 analyst Don MacLean questioned the play, saying Oregon State would "remember that." The postgame handshake between Tinkle and USC coach Andy Enfield was about as brief as it gets. The two teams are not scheduled to meet again this regular season but could face off again in the Pac-12 tournament.
UP NEXT: Oregon State hosts No. 11 Utah on Thursday.