St. Louis faced a one-run deficit heading into the bottom of the sixth, but the Cardinals struck in that inning against Paul Maholm and went on to win their second in a row.
Pete Kozma drew a one-out walk from Maholm (9-10) and went to second on a sacrifice by pitcher Joe Kelly.
Matt Carpenter, Beltran and Matt Holliday then produced consecutive doubles in the span of 11 pitches to give the Cardinals a 4-2 lead.
David Freese added two RBI for St. Louis on a groundout in the fourth and a single in the seventh.
Kelly (5-3) lasted six innings to get the win, giving up two runs on seven hits. Three relievers blanked the Braves on two hits.