Alex Burrows and Mike Hoffman each had a goal and an assist for Ottawa, which tied Montreal atop the Atlantic Division with 84 points.
Anderson earned win No. 147 with Ottawa and passed Patrick Lalime for the top spot.
Fredrik Claesson and Ryan Dzingel also had goals for the Senators.
Calvin Pickard stopped 27 shots and Matt Nieto and Sven Andrighetto scored for the Avalanche, who were eliminated from the playoffs with the loss. It is the third straight year they’ve failed to reach the postseason after posting 52 wins and 112 points in 2013-14.
Nieto gave Colorado a 1-0 lead with his fifth goal midway through the first period, but Ottawa gained control in the second. Goals by Claesson, Burrows and Hoffman in the second made it 3-1.
Dzingel scored at 11:22 of the third to seal the win.
The Avalanche were trying for their first three-game winning streak of the season, but couldn’t generate much offense after outshooting the Senators for most of the first period.
They went the final 28:27 of the game with only two shots. Andrighetto ended a drought of 17:28 without a shot when he scored in the final minute.
Ottawa outshot Colorado 20-6 in the final two periods.
NOTES: Senators D Mark Borowiecki missed his second straight game with an undisclosed injury. Second-leading scorer Mark Stone was out after suffering a lower-body injury against Arizona on Thursday. C Kyle Turris missed his third straight game with a fractured finger. … Avalanche C Matt Duchene has gone pointless in the past 10 games and has just one goal in his past 25. … Ottawa recalled Phil Varone from Binghamton of the AHL. … Colorado C Mikhail Grigorenko was scratched for the fourth time this season.
UP NEXT
Senators: Host Tampa Bay Lightning on Tuesday night.
Avalanche: At Arizona Coyotes on Monday night.