Carlos Emory also had 19 points, and Devoe Joseph and Garrett Sim scored 15 each for the Ducks (24-9), who rallied from a 15-point deficit in the first half to advance to the quarterfinals and a game against Pac-12 rival Washington in Seattle on Tuesday.
Oregon's 108 points was its most in a game since beating UC Riverside 108-67 Dec. 28, 2002.
Devyn Marble led the Hawkeyes (18-17) with 31 points and made all seven of his 3-point attempts. He shot 10 of 15 overall.
Oregon took the lead for good on a 3-pointer by Joseph with 11:44 to play in the game that made it 71-68.
Marble's 31 points were the most by the Hawkeye in the postseason since Ed Horton tallied 32 against N.C. State in 1989.