Lewis (12-10) allowed three runs on five hits over 7 1/3 innings to snap a personal four-game winless stretch. He struck out seven and walked one, as the Rangers beat the A's for a ninth straight time.
"It's all location...getting yourself into pitcher's counts instead of hitter's counts and keeping the ball down in the zone," said Lewis.
Brandon McCarthy (8-8) lasted six innings, surrendering four runs -- two earned -- on five hits to suffer the loss.
"We gave them extra outs and they took advantage of it," said Willingham.
Lewis, who is 4-0 in five starts this season against the A's, fell behind in the opening frame when Matsui drew a two-out walk and Willingham followed with his 24th home run of the season.
A half-inning later, runners reached the corners on a Kinsler leadoff walk and a McCarthy error before Beltre ripped an RBI double off the wall in left. David Murphy's subsequent sac fly tied the game.
In the fifth, Kinsler again got the Rangers going with a one-out infield single. He scored from first on Elvis Andrus' double to deep center. Later in the frame, Andrus scored on Scott Sizemore's throwing error to make it a 4-2 game.
Michael Wuertz spelled McCarthy in the seventh and consecutive RBI singles by Andrus, Young and Beltre gave the Rangers a 7-2 lead. Mitch Moreland added an RBI single off of Craig Breslow later in the inning.
As for Lewis, he exited after a one-out Jemile Weeks single in the eighth, having not allowed a runner to advance past first base since the opening inning. Mike Adams spelled Lewis and retired Coco Crisp before allowing a towering blast to Matsui.
Young's three-run double and Napoli's two-run homer off of Neil Wagner in the eighth capped the scoring and Neftali Feliz tossed a 1-2-3 ninth to end the game.
"They're better than us, there's no sidestepping it," said McCarthy. "They do a lot of things well and what they're doing is what we need to aspire to get up to."
Lewis has allowed an AL-leading 34 home runs this season. He matched a career-high with his 12th victory of the season...Josh Hamilton was scratched from the Rangers lineup to be with his wife for the birth of their fourth daughter...The A's have committed 115 errors this season, which is the most by an Oakland team since the 2001 club had 125...McCarthy had tossed back- to-back complete games in his two previous starts.