MONTREAL -- The third period has been of the Montreal Canadiens' best throughout the early season, a trend that is proving to be tough for opponents to handle.

Center David Desharnais' third-period goal stood as the game-winner as the Canadiens beat the New York Islanders 4-1 Thursday night at the Bell Centre.

"We just stuck to our game," said Canadiens right winger Dale Weise, who scored his eighth of the season. "We play a fast game, we play four lines, and I think that's tough for teams to handle when it gets into the third period. Teams get worn down. Their top pairing (defensemen) played a lot of minutes. We just stick to our structure and good things will happen for us."

Right winger Brendan Gallagher and center Tomas Plekanec also scored for the Canadiens. Right winger Kyle Okposo connected for New York.

Goaltender Jaroslav Halak stopped 20 shots for the Islanders (7-4-3). Goalie Mike Condon made 17 saves for Montreal (12-2-1).

It was the fourth consecutive game that New York was held to fewer than 25 shots and the second time in that stretch that the Islanders were held below 20.

"It's been the last couple of games where we haven't gotten that many shots," New York defenseman Johnny Boychuk said. "If we shoot more pucks to the net, get it on net and more bodies to the net, we'll fare better."

Montreal's revitalized power play put the home side ahead at 18:50 of the first period. P.K. Subban kept the puck from leaving the zone before lobbing it over to fellow defenseman Jeff Petry just inside the blue line on the left side. Petry aimed his shot toward Weise at the inner hashmarks, and the winger put his stick in place for the perfect deflection.

It marked just the second road power-play goal the Islanders allowed this season.

Center John Tavares, who returned after missing three games because of illness, nearly got his team on the board with the man advantage early in the second. Uncovered and with an open cage to Condon's left, he sent the puck behind the netminder, but it went through the crease to the other side.

Okposo tied it at 3:35 of the second period, moments after a New York power play expired. After taking the puck from Halak behind the Islanders' net, Boychuk sent a short pass to Okposo in his own end. Okposo skated down the ice along the left wing before cutting into the slot and beating Condon with a shot from just outside the circle.

Desharnais put the Canadiens ahead 2-1 at 6:22 of the third period. Defenseman Nathan Beaulieu's clearing attempt slid down the left side and hit linesman Michel Cormier just outside the Islanders' zone. Left winger Tomas Fleischmann picked up the loose puck and took advantage of a sliding defenseman Nick Leddy before feeding Desharnais with a cross-ice pass from the goal line.

Gallagher's sixth of the season put Montreal up by a pair a minute and a half later. Plekanec dropped a pass for left winger Max Pacioretty along the right boards, and Pacioretty skated to the top of the circle before snapping a shot that was deflected by Gallagher in front of Halak and trickled just past the goalie.

With the assist, Pacioretty snapped a five-game point drought.

"It was nice to contribute," said Gallagher, whose tally was his first since Oct. 29. "It was nice for the line. We just tried to stick with it, not change anything. We keep getting the chances, eventually it'll go in. Tonight we found a way to get one. Obviously, it feels good, and hopefully it can kick-start us."

Plekanec finished off the scoring into an empty net at 17:57 of the third.

"It's unfortunate because we go through these stretches where we play well and we don't get rewarded, and there were games that we've won and probably shouldn't have had any right getting the two points," Islanders coach Jack Capuano said. "But in a game like this, we were right there with a good team, on the road, great atmosphere, and unfortunately it is what it is."

NOTES: New York G Jean-Francois Berube served as Jaroslav Halak's backup for the second straight game. G Thomas Greiss was a healthy scratch. ... The Canadiens did not change their lineup, scratching RW Alexander Semin and D Jarred Tinordi. ... Montreal G Carey Price missed his third straight game with a lower-body injury. ... The game was the first of three meetings between the Canadiens and Islanders, all taking place within a 17-day span. ... The Islanders scratched RW Steve Bernier and LW Taylor Beck.