E.J. Singler added 15 points and nine rebounds for the Ducks (12-2).
Ahmad Starks had 22 points, and Roberto Nelson 18 for Oregon State (10-4).
Dotson, a freshman guard, scored seven points in Oregon’s 15-2 run to open the second half, helping the Ducks turn the tide and take a 43-36 lead.
Oregon State came right back, with Devon Collier scoring seven consecutive points to tie the game.
The Beavers took a 47-46 lead on Starks’ two free throws with 11:02 remaining.
But Oregon took the momentum for good, scoring nine straight points over 3 1/2 minutes. Arsalan Kazemi’s basket off an offensive rebound gave the Ducks a 55-47 lead with 7:34 remaining.
Oregon State got no closer than five after that.