All-Star starter Cody Bellinger hit his 27th home run of the season in the second inning. Muncy immediately followed with his 18th blast of the year to put the Dodgers up 2-0.
Alex Verdugo and Justin Turner hit back-to-back home runs in the fifth inning. Muncy added his second home run of the night in the seventh inning.
Los Angeles took a 9-8 lead on Chris Taylor's go-ahead RBI single in the ninth inning off Rockies closer Wade Davis. Enrique Hernandez extended the Dodgers' lead with a pinch-hit, three-run home run two batters later.
"Honestly, I think we're so deep offensively, that no matter the deficit or the team we're playing, we're going to hit," Bellinger said. "And if we're not hitting, it's not going to be for a long time."
Los Angeles moved to a major-league best 56-27 with Thursday's victory. The first-place Dodgers have a 13-game lead over the Rockies in the NL West Division.