Egor Sokolov (2) Shane Pinto and Lassi Thomson had goals for the Senators while Kevin Mandolese played the first two periods in goal. Like Saturday, Leevi Merilainen played the third period for the Sens.
Alexis Gravel was in goal for the Canadiens while Rafael Harvey-Pinard, Joshua Roy and Mika Cyr scored for the hosts.
"As long as we won the game, that's all that matters," Sokolov said. "The team had a pretty good pace and we took care of our defensive zone at the end and got the job done.
"A win is a win and we're moving on now."
Ottawa's positive start was finally rewarded at 14:33 as Sokolov deposited a rebound after a nifty move out front as Gravel couldn't contain Thomson's shot from the blue line.
The Russian would have his second of the afternoon with just 11.8 seconds left in the first as Shane Pinto's backhand pass through centre ice was hammered home on a one-timer from the right circle to give Ottawa a 2-0 lead after 20 minutes.
"I watched the shifts [from last game] and thought I was doing the right things on the ice," Sokolov said. "I always expect from me a little bit extra and create scoring chances … but I was missing a bit of offensive creativity but today, I was able to get some chances and score some goals."
In the blink of an eye the Sens' lead was 4-0 early into the second. Pinto made it 3-0 at 4:04 as he was left wide open in the slot to beat Gravel glove side off of a nice feed from Roby Jarventie before Thomson picked his spot with a gorgeous shot just 28 seconds later.
"During the summer I worked on a number of skills to make me a more offensive player and I think the last two games I've been showing those things," Thomson said.
Harvey-Pinard got Montreal on the board at 3:16 of the third on the power play after the Senators had taken a too many men on the ice penalty before a tip out front by Roy at 14:05 cut Ottawa's lead to 4-2.
Cyr made it a one-goal game with 1:15 left but the Sens rookies held on to complete the sweep.
"Those kinds of leads are a little bit scary from the coaching perspective because usually a goal creates momentum for the opposition and when they got their first one, you're still feeling ok but once they got their second, you really know you're in a hockey game," Sens head coach Troy Mann said. "Overall, it's great to win though and we had some good performances again tonight."
Mark Kastelic wore the 'C' for Ottawa while Sokolov and Thomson were named alternates.
Ottawa had beaten Montreal 4-3 Saturday at Canadian Tire Centre in game one of the series.
