Eller had a goal and two assists and Desharnais scored a pair to lead the Montreal Canadiens to a 6-1 win over the Buffalo Sabres.
"We've been struggling a bit the last couple of games so I think it was relief for Davey, too, to see the puck go in twice," said Eller of his and Desharnais' first goals of the season, just 28 seconds apart in the second period. "It's a great feeling to score and a great feeling to win."
After suiting up for the Canadiens' season opener, Eller was a healthy scratch the next two games. He returned to the lineup last Sunday, inserted on the wing with Desharnais and Erik Cole, with Max Pacioretty sidelined following an appendectomy a day earlier.
Desharnais, meanwhile, had struggled to find his breakout form from a season ago, a campaign that saw him pile up 60 points in 81 games.
"I've got to be better, I want to be better," he said. "There's nobody else that's going to feel sorry for me so I've just got to be better and I was tonight. I just want to keep going."
Carey Price made 30 saves for the Canadiens for his fifth win of the season.
The game marked the season debut for Montreal defenseman P.K. Subban, who signed a new contract Monday after sitting out the team's first four games while negotiations went on.
"When you're playing your first game and the team has a great start it's sort of a relief," said Subban, who picked up his first point with an assist on Desharnais' second goal. "I'm just happy with the win here today."
Subban admitted he didn't "feel too great" in his return, recognizing his timing was off. Canadiens coach Michel Therrien planned to ease the blue-liner into the lineup after his long layoff, dressing seven on the back end.
Subban finished the game with 18:01 of ice time, fourth among Montreal's defensemen.
"It's important for us to manage his return and his ice time. Unfortunately there aren't a lot practices available like the others had," Therrien said. "We felt the best way to get him back in was to dress seven defensemen.
"He did very well in his first game."
After a big win in a wild game against the Boston Bruins on Thursday, the Sabres (3-4-1) lost for the fifth time in their last six games. Goaltender Ryan Miller made 17 saves over two periods before being replaced in the third by backup Jhonas Enroth.
"We didn't have our `A' game right off the bat. We started in the second but it was too late," Sabres coach Lindy Ruff said. "It's a collective effort. You can't point fingers at anybody."
Bourque injected some life into what had been an uneventful first period with Montreal's 10th power-play goal of the season. Andrei Markov's stretch pass - tipped along the way by Tomas Plekanec - found Brian Gionta along the right boards. Gionta waited before passing it on to Bourque, who drove to the net for his second of the season.
Montreal took a 2-0 lead for the fifth time in its seven games early in the second. Gallagher and fellow rookie Alex Galchenyuk completed a nifty 2-on-1 that Gallagher capped with his third of the season as the puck went in off Sabres defenseman Christian Ehrhoff at 2:03.
Desharnais finally got his first at 10:08. Just seconds after Sabres forward Tyler Ennis hit the crossbar, the diminutive Canadiens center took a pass from Eller in the high slot and fired a shot past Miller.
Eller added to Buffalo's misery with his first goal of the season just 28 seconds later.
Plekanec set up Bourque's second goal of the game at 1:22 of the third. The Czech center showed patience on a 2-on-1, waiting out Buffalo defenseman Mike Weber's attempt to block the pass before easily placing it on Bourque's stick.
Thomas Vanek broke Price's shutout bid with a short-handed goal at 3:01.
Desharnais picked up his second of the season on the power play at 12:43.
NOTES: D Yannick Weber and F Ryan White were scratches for the Canadiens, who went with 11 forwards and seven defensemen. ... Therrien acknowledged "there's a chance" that Pacioretty, who practiced with his teammates on Friday, could be back in the lineup on Sunday. ... Buffalo's one shot in the first was its fewest in a regulation period since Oct. 7, 2011, against Anaheim when the Sabres had none in the third. ... Montreal last allowed one shot in a period Oct. 13, 2011, against Calgary.