Tkachuk gave Ottawa a 1-0 lead at 11:00 of the first period when he tipped in Zub’s point shot.
Giroux scored on the rebound off his own wraparound to make it 2-0 at 18:34.
Panarin beat Forsberg through traffic with a wrist shot from the point on the power play to cut it to 2-1 just 39 seconds into the second period. Mika Zibanejad extended his point streak to eight games (four goals, six assists) with the secondary assist.
“They’re a fast team,” Zibanejad said of the Senators. “They play fast and they took advantage of our, at times, sloppy play.”
Tarasenko elected to shoot on a 2-on-1 with Tim Stutzle and picked the top right corner short side to extend the lead to 3-1 at 5:13.
“It was great for ‘Vlady’ to score and score a highlight goal like that,” Ottawa coach D.J. Smith said. “It’s going to give him some confidence, and then he gets a second one. If you can get your top six rolling like that, you’re going to win some games.”
Forsberg stretched to make a pad save on Alexis Lafreniere, but Miller scored on the rebound to cut it to 3-2 at 5:35.
“That second period was run and gun: guys behind us, odd-man rushes,” Lafreniere said. “Just a sloppy one out of us and definitely one to forget.”
Batherson scored a rebound on the rush after Shesterkin saved Tarasenko’s shot to make it 4-2 at 7:18.
Tkachuk extended the lead to 5-2 at 17:43 when Zub’s broken-stick point shot bounced off the end boards to Tkachuk, who chipped it in at the side of the net.
“I think the changes that we’ve made over the last couple games are starting to show,” Tkachuk said. “Breakouts, neutral zone [play] and stuff like that, just little details to our game. So, I like where we’re heading and we just keep improving every single day.”