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.
NCAA title game hero Kris Jenkins said he will withdraw his name from the NBA draft and return to Villanova for his senior season.
Andy Katz breaks down the likelihood of Villanova, Syracuse, North Carolina or Oklahoma making a run to the Final Four next season.
Florida State has announced that Xavier Rathan-Mayes will return to the court for his junior season. The 6-foot-4 guard declared for the NBA draft last month but did not hire an agent.