Portland State hung around in the first half and trailed 37-29 at the break. The Zags went on a 10-0 run early in the second to build a 47-32 lead.
A basket by the Vikings' Scott Morrison and two straight 3-pointers by Lucas cut Gonzaga's lead to 55-48 with 5:55 left. It was their last field goal for more than 4 minutes.
Matt Bouldin hit two free throws as the Zags' lead increased to 57-48. Layups by Mallon and Jeremy Pargo made it 61-48 with 2:54 left, ending the Vikings' threat. Gonzaga outscored the Vikings 14-3 in the final 4 minutes.