Danton Heinen gave Boston a 1-0 lead at 3:01 of the first period, poking in the rebound of McAvoy’s shot at the front of the net.
Pastrnak took a cross-ice pass from Zacha on the rush and scored with a one-timer to make it 2-0 at 4:09.
Brandon Carlo finished off a quick passing play on a 3-on-1 to push the Bruins’ lead to 3-0 at 15:14.
“He makes people around him better,” Boston coach Jim Montgomery said of Pastrnak, who ranks second in the NHL with 24 points in 15 games. “As good a goal-scorer he is, he’s as equal passer, and the way he competes as a leader on our team and our most skilled player, it shows everybody that you have to work to have success.”
Oskar Steen scored top corner from the left circle to extend it to 4-0 at 4:07 of the second, and Hampus Lindholm made it 5-0 at 12:23 with a slap shot from the blue line on a power play.
NOTES: It was Pastrnak's 53rd career three-point game and his 141st road goal, tying Cam Neely for 11th and seventh, respectively, in Bruins history. He also became the 10th player in Boston history with 300 career road points. Ray Bourque leads with 689. … Bruins center Charlie Coyle played his 800th NHL game.