The result opened up the race in the West Coast Conference, where early in the campaign every team in the league has at least one loss.
The Pilots shot 51 percent from the field and converted on 8-of-14 shots from 3-point range. Portland built as much as a 17-point lead with 6:07 to go.
Pressley made 5-of-6 from the field and scored 16 points along with nine assists. Alec Wintering added 15 points for the Pilots and Kevin Bailey had 13.
Portland improved to 10-7 for the year and is 2-3 in league play.
Gonzaga (14-3, 4-1 WCC) was led by Sam Dower with 14 points.