With Canadiens defenceman P.K. Subban off for hooking, Clarke MacArthur scored a power-play goal 58 seconds into overtime to give his team a 4-3 victory on Saturday night.
Subban was handed two minutes for guiding Ottawa forward Erik Condra into the boards with 19 seconds left in the game. Subban took issue with the call afterward, suggesting it was "personal."
"It just didn't really make sense to me,"he said.
"Other than that, it seems like it's personal to me because it has nothing to do with the game. Based on the standard of penalties, I don't see a penalty there at all."
Montreal coach Michel Therrien also criticized the call.
"You all saw it," he said to reporters. "One thing is for certain, it's not P.K.'s fault. I support him."
Controversy aside, the Senators (19-18-7) have now won four straight.
Erik Condra, Colin Greening and Mark Stone also scored for Ottawa, which jumped out to a 3-1 lead in the first period at the Bell Centre.
Daniel Briere, in his best game with the Canadiens (24-14-5), scored twice and had an assist while Brian Gionta also had a goal.
Briere, who signed with Habs as a free agent this summer, was back in the lineup after sitting out as a healthy scratch for two games.
He began the game centring the fourth line but was put on the wing with Tomas Plekanec and Brian Gionta in the second period after a strong start.
"You try not to get caught up too much in it. You try not to think about it," Briere said of the line promotion. "It's a good feeling to be part of the team, to feel like you're helping out."
At the beginning of the third period, Briere brought his team to within one with a nifty move at the side of the net. He managed to jam the puck past Craig Anderson at 1:57 off a behind-the-net pass from Plekanec.
The Canadiens continued to press after his goal and put in another a few minutes later. Gionta shovelled in a loose puck at 4:46 off a point shot, after Plekanec and Briere had a crack at it first.
But it wasn't enough after Ottawa's quick start.
Greening quieted the crowd with a goal only 13 seconds into the game on a cross-crease pass from Condra.
The Canadiens had a few tough bounces to begin the game.
What looked like a power-play goal by Rene Bourque at 4:05 of the first period was called back after a quick whistle on a scramble in front. And they couldn't put the puck past Anderson on a lengthy 5-on-3 power play.
Briere finally tied the score 11:32 into the first period when he managed to knock in his own rebound after a pass from Travis Moen.
The tie didn't last long, though, as the Senators regained the lead at 13:50 on a backhand shot from Mark Stone in only his second game of the year since getting called up from the AHL.
Condra scored again for the Senators 14 seconds later on a pass that went off the skate of Habs defenceman Francis Bouillon.
Heading into the second period with a two-goal lead, the Senators played a more conservative style and were able to limit the chances on Anderson. Both teams had just seven shots apiece in the second period.
Paul MacLean said the team got "a little tentative" to start the third and gave the Canadiens too much space.
"We knew they were going to come with a push to start the period and we didn't defend our net as hard or as diligently as we should have," he said.
"But I thought after that we came back and slowly started to establish some play in their zone."
Condra said the Senators have started to do the little things that have helped them put together four wins in a row.
"They ended up taking a penalty at the end (of the third period) and we capitalized," he said.
"It's big for us. A few times this year we've let up late goals and folded and let teams beat us. This time we held on strong and ended up coming up with the victory."
NOTES: Senators captain Jason Spezza missed his fourth straight game with a hip flexor injury. ... Canadiens defenceman Raphael Diaz was a healthy scratch for the first time this season.