The win pushed the Cougars' home winning streak to 40 games, which is the second longest active streak in the nation.
Leading 38-27 at the break, BYU (12-4, 1-0 Mountain West) scored the first 12 points of the second half during a 17-3 run that stretched the lead to 55-30 with 15:50 remaining. The Rams never seriously threatened after that.
In the first half, Plaisted scored 8 points during a 12-2 BYU run that propelled the Cougars to a 25-10 lead with 8:10 remaining.
Colorado State (6-10, 0-2) answered with a 15-4 run of its own that included six points off the bench from Ronnie Aguilar that pulled the Rams to within four at 29-25. That was as close as the Rams would get the rest of the evening.
The Cougars won despite shooting only 52 percent from the free throw line, which was only slightly better than their 49 percent from the floor.
BYU outscored the smaller Rams 39-10 in the paint.
Lee Cummard chipped in 10 points for the Cougars and pulled down 9 rebounds.