Three batters later, Harris hit a 417-foot homer to straightaway center. The nine-run inning was the biggest for the Braves since Sept. 9, 2020, when they scored 11 times in the second inning of a 29-9 win over the Miami Marlins.
Ozuna hit a two-run homer in the sixth.
Aaron Bummer (2-2), the first of five Braves relievers to follow Carlos Carrasco, tossed 2 1/3 scoreless innings.
Carrasco gave up six runs in two innings. Pete Alonso had a two-run single and Cedric Mullins lofted a sacrifice fly in the first before Juan Soto hit a 407-foot, two-run homer and Jeff McNeil had an RBI double in the second.
Peterson surrendered a season-high six runs over a season-low 3 1/3 innings. The Mets have lost 12 of 14.
Key moment
Harris' grand slam was his first since last Aug. 14.
The Mets gave up at least nine runs in an inning for the ninth time in franchise history and the first since Apr. 16, 2019, when the Philadelphia Phillies scored 10 runs in the first inning of a 14-3 win.
The three-game series concludes Thursday night, when Mets RHP Kodai Senga (7-4, 2.30 ERA) opposes Braves RHP Bryce Elder (4-9, 6.12).
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AP MLB: https://apnews.com/hub/mlb