Davis, who leads the majors with 97 RBIs, drove in a pair of runs with a sixth-inning double and another with a sacrifice fly in the first inning.
"I think it's huge anytime you swing the bats well at the beginning of the game," Davis said. "It puts some pressure on the opposing pitcher and gives you more opportunities.
"The way we're swinging the bats we know that if one guy doesn't do it, the next will do it. We're getting on base, running the bases well and we're taking advantage of every opportunity."
Hardy homered, his 17th of the season, in the four-run sixth with Davis aboard. He picked up another RBI in the third when Davis scored on his ground out.
"Getting a lot of base runners and getting some timely hits, it's a good combination," Hardy said.
"We had a lot of opportunities to score more, too. We got a lot of guys on-base early, with hits and walks, Nate (McLouth) leading it off sets the tone. And he's stolen 25 bases, too. That puts pressure on the pitcher to be quicker to the plate which helps the hitters and it puts pressure on the defense."
The Orioles' 18-hit attack matched their season high and included seven players with multi-hit games, including three each by rookie Henry Urrutia, Nick Markakis and Hardy. McLouth reached base five times -- two hits and three walks.
"Henry had some great at-bats," Orioles manager Buck Showalter said. "J.J. had the homer. Nate was on base all night. Chris settled back in pretty good. It was good offense all night."
Feldman (2-1), who was acquired in a July 2 trade from the Chicago Cubs, was the beneficiary of the offense, picking up the victory.
"It's a great way to open the second half, clicking on all cylinders," Feldman said. "The offense has been great. The defense has gotten the job done and now the pitching is getting it going."
Feldman limited the Royals to five singles and two runs over eight innings.
"I was just throwing strikes," Feldman said. "I kind of got away from it in the fourth inning and walked some guys, then we got back to it, and let the defense do the work behind me."
Royals manager Ned Yost summed up the defeat in four words: "It was a clunker."
Davis has lost his past four starts with a 10.91 ERA in that span, giving up 21 runs and 24 hits and 12 walks. Davis has only one win in his past 11 starts.
"I'm just inconsistent," Davis said. "I've got to get deep in games. I fell behind in the count too much, a leadoff walk."
Mike Moustakas committed a fielding error in the first inning, ending the Royals' streak at 11 games without an error, which matched a club record. Moustakas' error on Manny Machado's hopper led to two unearned runs.
"I just missed it," Moustakas said. "No excuses for it. It's routine as it gets. It's a 5-4-3 double play and I just didn't make the play. That's an additional 20 pitches for Wade. It's going to sting for a while."
RHP Felipe Paulino, who had Tommy John surgery last July and remains on the 60-day disabled list, threw 25 pitches to hitters without shoulder soreness that had plagued him recently. ... The Royals acquired OF Gorkys Hernandez from the Marlins in a minor league trade. Hernandez hit .192 in 70 games last season with Pittsburgh and Miami. Hernandez, who hit .275 in 90 games this season with Triple-A New Orleans, was assigned to the Royals' Omaha club in the Pacific Coast League. ... Orioles RHP Jason Hammel, who starts Tuesday, is 6-2 with a 4.25 ERA in 11 road starts.