Joe Burton added 17 points, seven rebounds and 10 assists for Oregon State (12-11, 2-8 Pac-12), which recorded its highest point total in a conference game this season.
Brandon Taylor had a season-high 21 points and six assists, and Jarred DuBois scored 20 points, for Utah (10-12, 2-8).
Oregon State bumped its nine-point halftime lead to 18 less than 7 minutes into the second half. The Beavers scored eight straight points, the last two on a Challe Barton lay-in off a Burton assist with 13:20 left, to make it 47-29.
Utah came back with a 12-2 run, the last five points by Taylor, to close within 49-41. Nelson scored the next five points to give Oregon State a 13-point lead with 8:52 remaining.
The Utes next play at Oregon Saturday.