The Ducks outscored the Eagles 20-8 in the final 7:42, taking advantage of Eastern Washington's depleted lineup after three starters fouled out over a three-minute span midway through the half.
Oregon (1-1) took its first lead of the second half on a layup by Tony Woods to make it 58-57 with 6:22 left. Sim delivered the biggest blow, draining a 3-pointer to extend Oregon's lead to 65-58 with 5:13 to play.
Oregon had 21 turnovers but just one in the final 10 minutes. Its 13 turnovers in the first half led to 20 points for the Eagles, who led 39-34 at the break.