The Athletics' No. 2 prospect yielded an unearned run on three hits over six innings as Triple-A Sacramento bested Salt Lake, 7-1.
Peacock retired the first 10 batters in order before Chris Iannetta smacked a one-out double in the fourth inning. The 23-year-old right-hander was his own worst enemy in the fifth, allowing a double to Trevor Crowe and advancing him to third on an errant pickoff throw. Crowe came around to score when Peacock threw a wild pitch with two outs in the frame.
"I had a good changeup, a good curveball and a good fastball. I was locating it well," said Peacock, who was 1-5 over his last 10 starts.
Peacock (8-7) also ran into trouble in his last inning, loading the bases on a double, a walk and a hit batsman with one out. But he got No. 12 Angels prospect Kole Calhoun to hit into a 4-6-3 double play.
"I got a little wild and wasn't able to locate as well as I was the rest of the game, but I was able to get the double-play ball," he said.
Peacock's night was finished after 71 pitches, 46 for strikes. The low pitch count was part of the plan, according to the hurler.
"They limited my pitches tonight, because I had thrown a lot of pitches in my last two starts," he said. "I'm actually pretty happy about that."
After getting off to a strong start in the Pacific Coast League with a 3.49 ERA in five April starts, Peacock has struggled. The Florida native has allowed 61 earned runs over his last 16 starts and sports a 6.25 ERA this season for the River Cats.
MLB.com's No. 62 prospect has struck out 111 batters in 103 2/3 frames this season, the third straight Minor League season in which he's averaged more than a strikeout an inning. Wednesday's low total of four was something of a surprise, but Peacock said it was intentional on his part.
"I was pretty much pitching to contact," Peacock said. "I wanted to try something different. Things this year haven't gone so well, I was trying to change it up, I guess.
"The strikeouts will come, but yeah, I'm going to try and pitch to contact more and go deeper into the game. I'd rather go eight innings than strike out a lot of guys."
Grant Green, Oakland's No. 5 prospect, was 3-for-5 with a pair of doubles and two RBIs while Stephen Parker slugged a three-run homer for the River Cats.
Arnold Leon tossed two perfect innings of relief and Pedro Figueroa pitched a 1-2-3 ninth for Sacramento.
Iannetta finished 1-for-3 with a walk in his rehab outing and Vernon Wells was hitless in three at-bats for the Bees.