UCLA (25-9) couldn't keep up with the hot-shooting Ducks without freshman Jordan Adams, who sat on the bench with a boot on his right foot after breaking it in the semifinals against No. 18 Arizona.
Larry Drew II had 14 points and six assists, but had five turnovers for the top-seeded Bruins, who may have lost a chance to play in the West Regionals at the Staples Center in Los Angeles.
Shabazz Muhammad had 14 points and Norman Powell had 10 in Adams' place for UCLA.
Adams brought the Bruins back from an 11-point deficit by himself against Arizona in the semifinals, scoring 17 of his 24 points in the final 9:57 15 straight at one point in UCLA's 66-64 win.
The Bruins withstood a last-second flurry by the Wildcats, but Adams didn't; one of Arizona's players came down on his foot, breaking the fifth metatarsal. That left the Bruins without their second-leading scorer (15.3 points) and dimmed their hopes the rest of the postseason.
Oregon beat UCLA by nine in their lone meeting during the regular season, but was shaky on the big stage at first, with turnovers on its first four possessions and six in the opening 3 minutes.
Once the Ducks settled down, they settled in, hitting their first five 3-pointers during a 17-4 run that put them up 23-18.
Oregon kept hitting from the perimeter 7 of 9 from the arc and led 41-32 at halftime.
But trailing by double figures is nothing to the Bruins; they had done it in every game this tournament.
Muhammad got UCLA started in its two previous rallies after struggling in the first half and did it again. Held to three points on 1-of-3 shooting, the fab freshman scored seven points in the opening 4½ minutes, pulling the Bruins within 49-46.
Oregon kept its composure, though.
The Ducks scored six straight points and did a better job of containing Muhammad.
Storylines Oregon 78, No. 21 UCLA 69
R Oregon's Carlos Emory leads with 20 points.
• The Ducks go 7 of 14 from 3-point range.