O'Day finished with 9-of-11 shooting from the field for the Catamounts (15-10, 10-2 America East Conference). Hector Harold added 15 points and six assists, Cam Ward had 14 points, Kurt Steidl had 11 and Brandon Hatton 10.
Vermont went up 15-2 early on a Steidl 3-pointer and the Catamounts dominated the first half - sinking a total of 11 from distance - to lead 57-19 at the break. UMass Lowell made only seven buckets in the period.
The Catamounts continued to hit from beyond the arc in the second half - finishing with 16 of 21 (76.2 percent) - and led by as many as 49 points with 4:33 to play.
Chad Holley led the River Hawks (10-15, 4-8) with 16 points and three rebounds.