The Blues' defense has put last season's scoring drought behind them.
"We didn't exactly go end-to-end and go top shelf," said McKee, who scored his first goal of the season. "It was just to the basics, getting pucks to the net and tonight, we were fortunate to have three shots from the point go in. We want to add to the offense as much as we can."
St. Louis' defenders have four goals in four games this season after tallying just 15 in 2007-08.
Keith Tkachuk and Brad Boyes each scored for the fourth straight game for the Blues, who have won three of their first four games. Yan Stastny scored, and Boyes also had an assist and Paul Kariya added a pair of assists. The Blues last scored six goals in a game Jan. 8, 2008, 6-1 over Columbus, a span of 45 games.
Manny Legace stopped 29 shots to improve to 3-0 on the season.
"We were fresh, waiting for them," Blues coach Andy Murray said. "We played a team that played (Wednesday) night and had a battle (against Nashville). We took advantage."
Dallas, which won its first game of the season Wednesday night at home against Nashville, got a goal from Krys Barch. Goalie Marty Turco, who came in with a 9-4-2 record and a 1.88 GAA against St. Louis, gave up five goals on 18 shots before being replaced by Tobias Stephan for the third period.
"Our goaltending has been poor," Stars coach Dave Tippett said. "Our top players are not playing with the commitment you need to win hockey games."
The Stars have won once in four games and have not displayed the intensity that helped them reach the Western Conference Finals a season ago.
"Our passion wasn't at the level it needed to be," Stars captain Brenden Morrow said.
Leading 2-1 after the first period, the Blues broke the game open with three consecutive goals by Stastny, Boyes and Wagner.
Stastny got his first of the season 2:57 into the period to make it 3-1, banking a shot off a surprised Turco, who lost sight of the puck. Boyes got his fourth of the season on the power play at 12:59 while the Blues were on a 5-on-3 power play and Wagner got his first on a shot from the left point, beating Turco at 17:20.
"They were shooting and scoring, our defensemen tonight," Murray said. "You see Steve Wagner and Jay McKee stepping up. The key to those two goals: We had great screens at the front of the net. I don't think Turco saw either one of those shots. ... We talked about using our points because of the way they play defense."
Tkachuk opened the scoring at 12:47 of the first, picking off Mike Ribeiro's pass and beating Turco between the pads to give the Blues a 1-0 lead. McKee picked up his first of the season to make it 2-0 at 15:11.
Barch made it 2-1 with a tip-in goal at 16:46, his first of the season by redirecting shot from the point by Trevor Daley past Legace.
Brewer scored the Blues, second power-play goal of the game at 12:49 of the third period, beating Stephan with a long one-timer from the blue line.
Notes@: The Blues came into the game as the top-ranked power-play unit, going 7-for-14 through three games. They were 2-for-4 Thursday. They ranked last in the league a season ago at 14 percent. ... Stars F Mike Modano played in his 91st career game against the Blues, most against any other team. ... Blues F Kariya, who earned an assist on Boyes' goal, turned 34 on Thursday. ... Blues F Lee Stempniak (knee) sat out his third straight game. F Dan Hinote (thigh laceration) also sat out for St. Louis, while F D.J. King (wrist) made his season debut. The Stars were without forwards Jere Lehtinen (groin) and Steve Ott (undisclosed injury). ... The Blues began a seven-game homestand Thursday, their longest of the season.