Yoenis Cespedes drove in a career-high five runs, and Josh Donaldson scored a career-high four runs, as the persistent A's racked up 12 hits and nine walks against Indians pitchers.
Loading up with lefties to face Masterson (2-3), the Athletics reached base every inning against him. For that matter, the A's had at least one runner in every inning except the ninth.
Not only did the A's hit Masterson and almost every other Cleveland pitcher, they hit them hard. Oakland hit seven doubles, with Cespedes and Brandon Moss each hitting a pair of them.
"We'll take it," manager Bob Melvin said of all the doubles. "It doesn't matter how you score. I mean, Brandon Moss' at-bats are unbelievable, getting good swings against lefties. Donaldson, Cepsedes, all the guys we rely on to drive in runs are doing what they're supposed to do."
Oakland scratched out a run in the second inning, when Lonnie Chisenhall threw a Cespedes grounder past first base near the photography pit. But the real damage came later.
Donaldson and Moss drew walks to lead off the fourth, and back-to-back hits by John Jaso and Josh Reddick brought them home.
Donaldson and Moss came back up an inning later, knocking back-to-back RBI hits. When Cespedes doubled both home, Masterson's afternoon came to a close.
Masterson struggled with his command, but the A's tipped their hats to a guy they know can be really nasty.
"I don't know how he throws strikes, period -- just for the fact his ball moves so much," Donaldson said. "I mean, he does a great job of throwing strikes. But, for me, he's the hardest person in the game for me to hit -- because his fastball is running in on my hands constantly and he's throwing them three feet behind me, and he's got that slider.
"There's a big difference between his fastball and his slider. You can't hit both of them. You have to try to hit one. Today, we were fortunate enough to get some guys on base and take advantage of it."
Oakland scored seven runs on seven hits and five walks against Masterson, taking pressure off Jesse Chavez.
Chavez (4-1) worked well on the fringe of the strike zone, catching four of his six strikeout victims looking. But because so many Indians hitters put together long at-bats, Chavez logged only five innings before checking out at the 109-pitch mark.
Chavez worked hard early, relying on his curveball instead of his cutter. A night after Oakland needed 7 2/3 innings from its bullpen, following Scott Kazmir's ejection, Chavez was hoping to give the 'pen an easy day.
Thinking too much, he said, is what got him in trouble.
"It was one of those days where I had to rely on [my curveball] to get me through it," Chavez said. "I really didn't establish any of the other three [pitches] in the first two innings, which kind of hurt -- especially with what happened yesterday.
"I was trying to go [as] deep as I could into the game -- and me trying too hard kind of led to that in the first two innings."
Coming in with a 9-2 lead in the sixth, former closer Jim Johnson gave the Indians their best chance to get back into the game.
With a runner on first and two outs, Johnson walked three straight Cleveland batters, leaving a bases-loaded jam for Fernando Abad to clean up.
"[Johnson] was throwing strikes early on, [but] after walking three batters in a row, he's just not commanding his fastball like he's supposed to," Melvin said.
Abad struck out Ryan Raburn, and the Indians never had another runner in scoring position until the ninth.
The A's completely dominated the series, from plating eight runs in the second inning of Friday's opener to the final out on Sunday -- outscoring Cleveland, 30-6, in the three-game set.
"They've got it going, right now," Indians manager Terry Francona said. "They have good starting pitching, a very good bullpen, and they're swinging it from one through nine."
The total package -- good pitching, solid defense, and a prolific offense -- has the A's believing in themselves. But the way Oakland swings the bats has set the tone.
"I would just use the word, 'confident,' everybody's just going up there, taking good swings, recognizing pitches, working counts," Moss said. "We go through spurts where we try to force issues. But, for the most part, we've been a confident offense. Guys put together some really good at-bats that [have] some pop, and that usually leads to runs."