Fischer has drained nine 3-pointers in a game earlier this season and launched 11 of his 16 field goals Saturday from long range. Zac Seljaas added four treys as the Cougars (10-5, 1-1 West Coast Conference) made 48 percent of 3-point shots (11-23).
Collinsworth converted 12 of 17 free-throw attempts and added five field goals plus dishing eight assists.
Jacob Lampkin led Pacific (3-10, 2-2) with 14 points on 7-for-8 shooting. The Tigers rallied to a 41-41 tie on a Ray Bowles basket with 14 minutes left, but he missed the plus one after being fouled on the shot.
BYU roared ahead on a 14-2 run that featured 3s from Fischer and Seljaas and a Nate Austin dunk. Six of BYU's last 10 baskets were 3s.