Craig Anderson stopped Anze Kopitar in the shootout, then received a little help when Ryan Smyth's shot clanged off the post to end the game.
Ersberg thwarted Hejduk's shot in the shootout, only to be beaten through the legs by Mueller and to the glove side by Stewart.
After Stewart's goal, Ersberg slammed his stick against the post, causing his water bottle to pop off.
Kopitar, Drew Doughty and Alexander Frolov provided the offense for the Kings, who had their two-game winning streak end. Jack Johnson scored in the shootout.
Los Angeles had trouble generating any sort of offense against the Avalanche early on, being outshot by a 27-11 margin through two periods.
But the Kings roared to life in the third, starting with Doughty's goal 40 seconds into the period.
They kept the pressure up from there, leading to Frolov's tying goal with 1:21 left in regulation after the Kings pulled Ersberg to get an extra attacker on the ice. The Avalanche already had Brett Clark in the box serving a penalty for holding.
In addition to his contribution in the shootout, Mueller also had two assists, giving him 15 points in 11 games since being acquired from Phoenix in early March. He had 17 points in 54 contests while with the Coyotes this season.
At the morning skatearound, the Avalanche preached the importance of a fast start against Los Angeles.
They received just that in snapping a three-game winless streak.
Colorado erupted for three goals in the opening period, with a little help from some shaky defense in front of the Kings' net.
Hendricks got things rolling as he skated behind the goal and sent a pass in front of the net, the puck hitting some traffic and trickling into the goal through Quick's pads. Soon after, Kopitar tied it with a backhander over a sprawled-out Anderson.
The game took a gruesome turn midway through the period when defenseman Scott Hannan had his face bloodied by the stick of Brad Richardson.
Hannan stayed down for a moment, then lifted up his head, blood dripping to the ice near the Avalanche goal. Hannan was helped to the bench while holding a towel over his face.
Richardson drew a double minor for high-sticking, and the Avalanche quickly capitalized.
Hejduk slapped in a pass from Mueller, helping the team snap an 0-for-11 power-play drought.
Later, after a delay-of-game penalty, the Avalanche scored another power-play goal. Stastny was credited with the goal, even though he was simply sending a pass across the ice. Doughty tried to deflect the puck with his skate, only to send it past Quick.
Doughty slammed his stick to the ice in disgust, while Quick headed to the bench as Ersberg came on to replace him. It was Ersberg's first action in net since Feb. 11. He finished with 14 saves.
Avalanche forward Darcy Tucker served a one-game suspension for tripping Kings defenseman Matt Greene on an icing play Monday night. Greene was a scratch Wednesday night with an upper-body injury.
NOTES: Colorado F Brandon Yip skated with the team Wednesday morning. He's been out since hurting his shoulder March 1 against Detroit. ... Hannan returned to the ice midway through the second period. ... Kopitar has 33 goals this season, establishing a career high. ... Doughty has been a thorn in Colorado's side in recent days. On Monday, he scored in overtime against the Avalanche.