Jerod Lucas scored 17 points to lead the Beavers (1-8, 0-2), who haven't won since their opener against Portland State.
Arizona fell behind 13-7 early, responded with a 16-0 run capped by Mathurin's three-point play and steadily pulled away, never relinquishing the lead. Oregon State got within six points early in the second half, but a layup by Azuolas Tubelis made it 52-41 with 17:13 left and the Beavers didn't get within 10 points the rest of the way.
Kerr Kriisa finished with 11 points for Arizona and Tubelis scored 10.
The Beavers were thwarted by turnovers, with 22 that Arizona turned into 27 points.