Chris Odofia and Cam Griffin added 14 points apiece in the win, which sends the Pioneers (22-9) to a second-round meeting with Maryland.
Olson hit 5-of-9 shots from the field and Griffin secured 10 of Denver's 23 rebounds.
Sixth-seeded Ohio (24-10) had 35 rebounds and shot 41.5 percent from the field, but could not keep pace with the Pioneers' blistering 53.7 percent.
D.J. Cooper led Ohio with 16 points and Reggie Keely scored a dozen. Ivo Baltic scored only two points off the bench but had 15 rebounds.
Ohio led 32-30 at halftime but Denver made a 6-0 run late in the game to take the lead for good.