Garcia (12-7) allowed three runs on eight hits to earn the win. He struck out four and did not issue a walk.
Albert Pujols and Yadier Molina both had an RBI single for the Cardinals, who won Friday's series-opener, 4-3, on Nick Punto's 10th-inning sac fly. They have won four straight to climb within 5 1/2 games of Atlanta in the NL Wild Card race. With the Brewers 3-2 loss to the Phillies on Saturday, St. Louis moved within six games of the NL Central lead.
"Obviously you don't like where you are in the standings, but guys are playing loose and nobody's stressing out about it," said Berkman. "We understand what is in front of us. If we want to make a run it absolutely has to be right now."
Derek Lowe (9-14) surrendered four runs on nine hits over six innings to suffer the loss. He walked two and fanned six.
Freddie Freeman hit a two-run homer for the Braves, who have lost seven of their last 10 games.
St. Louis picked up where it left off on Friday, as Rafael Furcal singled to begin the home first, stole second, advanced to third on Jon Jay's sac bunt and scored on Pujols' base hit to left. Pujols moved to second on Berkman's single and scored on Freese's two-out double.
Consecutive doubles by Matt Holliday and Berkman pushed a run across in the bottom of the third and Molina followed two batters later with an RBI single up the middle, giving the Cardinals a 4-0 lead.
"I just look back and I made some bone-headed pitches to Holliday and Berkman," said Lowe.
A half-inning later, Freeman made it a 4-2 game with his 19th homer of the year. The blast to left plated Dan Uggla, who began the frame with a single.
In the fifth, Michael Bourn singled, stole second -- his major league-leading 52nd steal of the season -- and scored on Brian McCann's single to pull the Braves within a run.
They would get no closer, however, as Marc Rzepczynski tossed a scoreless seventh and Fernanado Salas faced the minimum in the eighth before handing the ball to Motte.
Heyward worked a one-out walk off of Motte, and with two down, stole second and advanced to third on Molina's throwing error, but Bourn flew out to right to end the game.
The Cardinals lead the season series over the Braves 4-1 with one game remaining...Lowe surpassed the 2,500 innings pitched plateau in the fourth. He has never been on the disabled list and ranks sixth among active pitchers in innings pitched.