Colorado State, at 14-4 and 4-2 in the Mountain West Conference, is now off to its best conference start since the league formed in the 1999-2000 season.
The lead changed hands 10 times. Colorado State took a 55-54 lead after a jumper and a 3-pointer by Gilling in the second half.
Trent Plaisted made the first of two free throws to pull BYU (13-6, 3-2) even at 55-55 before Tyler Smith made a layup to retake the lead for the Rams with 12:16 to go. Colorado State never trailed again.
The Colorado State bench outscored BYU's bench 23-6.