The defending World Series champions improved to 4-1 with an offense that hasn't missed Albert Pujols so far.
Only 20 pitches into the game, Reds starter Homer Bailey (0-1) trailed 4-0. It was the second time this season that St. Louis hit three homers in an inning. Molina also doubled home a pair of runs in the eighth.
Westbrook (1-0) overcame an early bout of wildness, allowing only three hits and one unearned run in seven innings. The right-hander slimmed down in the offseason and had an impressive spring training, getting the sink back on his fastball.
Both starters had a rough time early on a windy, 64-degree evening.
Bailey retired the first two Cardinals, then came apart. Holliday homered, Lance Berkman walked and Freese homered. Molina also homered on the next pitch, prompting Bailey to stand by the side of the mound with both hands scrunched on his hips in disbelief.
Freese, the World Series MVP, has hit safely in every game this season.
After the bad opening inning, Bailey settled in and allowed only two more hits while pitching into the sixth inning. Molina broke the game open with his double off Jose Arredondo in the eighth, which brought boos from the crowd of 16,909 that remembers his role in a brawl with second baseman Brandon Phillips two years ago.
Westbrook was pitching for the first time in nine days, and it showed in his control. Ten of his first 12 pitches were out of the strike zone. He walked four of the first 10 batters he faced, but didn't allow a hit until Phillips singled with two outs in the fifth.
Phillips came around to score when Zack Cozart hit a comebacker that Westbrook knocked down with his glove. Westbrook retrieved the ball, but threw wildly toward first base for an error that allowed Phillips to score.
The All-Star second baseman got a cramp in his left hamstring as he scored and left the game as a precaution.
Berkman wasn't in the Cardinals' original lineup because of a sore right hand. He took a few swings pregame and felt fine, getting back in the lineup at first base. He singled, struck out twice and walked twice.
The Cardinals wanted Berkman in the lineup - he has 23 homers at Great American Ball Park, the most by a visiting player.
NOTES: Kyle Lohse makes his second start for the Cardinals on Tuesday night. Lohse took a no-hitter into the eighth inning of a 4-1 win over Miami last Wednesday. ... Mike Leake makes his first start for Cincinnati. He pitched four innings in an exhibition against the club's minor leaguers at Great American last Tuesday. ... Cardinals SS Rafael Furcal dived in the hole to get a grounder and threw to second for a forceout while still on his back. ... Furcal was held hitless for the first time this season.
Link to Boxscore: St. Louis 7 at Cincinnati 1