Montana State (9-7, 4-1) led by just two points at the half, but opened up the second with a 15-5 run to go up 40-28 with 13:03 left to play. Egwuonwu shot 6 of 11 from the floor.
The Bobcats had nine players score to combine for 27-of-60 shooting (45 percent).
Northern Colorado shot 1.8 percent better (46.8 percent), but Montana State took 13 more shots than the Bears did and finished with four more 3-pointers. The Bobcat's bench outscored Northern Colorado's 28-15.
The loss snapped a four-game winning streak in conference play for the Bears.