Oregon State (10-7, 2-3) controlled the game throughout. The Beavers burst out to a 13-6 lead in the opening minutes and never saw their lead dip beneath five.
"Everybody is really down. We've really struggled these last couple of weeks," said coach Dana Altman.
For the second straight game leading scorer Joseph Young struggled to score, but was this time joined by the remainder of the starting line-up. The Duck starters shot just 7-for-35, and combined for 25 of the team's 72 points.
Mike Moser was just 3-for-15 from the field.
"You've got three starters, who are your three leading scorers, not shoot it well," Altman said. "We've been riding them all year, it's kind of hard when they don't shoot it well."
"A little bit of that was the pressure of trying to get it going."
With Oregon (13-4, 1-4) searching for answers on offense, Oregon State was able to take advantage on the other end. OSU opened the game 9-for-12 from the field, and for the fourth straight game, their opponent outshot the Ducks.
The Oregon State lead ballooned to 16 points at one point late in the first half, but the resilient Ducks were within 71-66 with 1:46 to go. At that juncture, sophomore guard Damyean Dotson ran down an errant Beaver pass, and with a wide-open lane to the basket lost his footing.
OSU retained possession and Roberto Nelson caught the defense unaware on a backdoor cut that sealed the deal.
"We're not doing the little things. We kind of got away with it for a while," Loyd said. "There's just some things we've got to fix.
While the Duck defense struggled to begin the game, they were much better to close the first half and for portions of the second.
Still, it was not good enough, and the Ducks will seek an end to the bleeding on next week's road trip in Washington.
"Each loss it gets tougher and tougher to get out of this hole we're digging. This is four in a row, and we're going to try and put it behind us," Johnathan Loyd said.
"We're going to bounce back. Is it going to be easy? No, and we may go through some more heartaches," Altman said. "But eventually, I think we will." Reserve Jason Calliste led the team with 17 points, and other bench players Richard Amardi and Ben Carter chipped in with 13 and 11.