The Ducks (27-8) led virtually the entire game, taking a 37-26 advantage into halftime and staying ahead by double digits throughout the second half.
Oregon will take on Midwest Region No. 4-seeded St. Louis in a third-round game Thursday. Oklahoma State was sent home with a 24-9 record.
The Ducks had a couple of first half spurts that gave them an advantage. Arsalan Kazemi had half of the Oregon points in an 8-0 run -- a dry spell of nearly 6 minutes for Oklahoma State -- for a 19-12 lead.
Dotson started a 9-2 run with a 3-point shot that ended with the Ducks up 28-18.
Dotson's 17 points led all scorers but Dominic Artis added 13 and Kazemi had 11 points and 17 rebounds.
Markel Brown paced Oklahoma State with 16 points but the Cowboys' star Marcus Smart wound up with 14 on 5-of-13 shooting.