PHILADELPHIA -- Old-school Daniel Mengden pitched like an old-time ace.
"It felt great," Mengden said. "We dream about doing it since we're little and coming all the way up and doing it is a great feeling."
Mengden (1-1) struck out seven and walked none to record his first career shutout in his 18th start. J.P Crawford had both hits off Mengden.
Using a herky-jerky delivery and wearing a handlebar mustache, Mengden kept the Phillies off-balance with a heavy dose of offspeed pitches and low 90s fastballs. He entered the game with a 2-10 record and 6.59 career ERA. It was the first complete game by the A's this season.
"Mengden really stymied us," Phillies manager Pete Mackanin said. "He pitched backward, threw as many offspeed pitches as fastballs. Give him credit. Glad I didn't give Crawford the night off."
The 24-year-old righty cooled down Rhys Hoskins and a hot-hitting lineup that scored 27 runs in a three-game sweep over Miami. Hoskins, who hit 18 homers in his first 34 games, was 0 for 3 with two strikeouts.
"He threw a lot of strikes, got ahead and as the game went on, you could see his confidence grow and grow," A's manager Bob Melvin said. "When he's got everything working, there's a gap between his off-speed stuff and his heater and it's tough to think along with him."
Phillies starter Mark Leiter Jr. (3-6) allowed four runs and seven hits, striking out nine in six innings.
"I thought the two homers put us in a tough hole early on. That was disappointing," Leiter said. "After that, I tried to keep us in it."
Olson hit a shot four rows shy of the third deck in right-center in the first inning, giving the A's a 2-0 lead on his 19th homer. The blast was estimated at 483 feet.
Joyce drove his 24th homer out to right-center in the second for a 4-0 lead.
Mengden also got his first career hit , a single off Crawford's glove in the shortstop hole before Joyce connected.
"I love hitting," he said. "Just try to get a good pitch to hit, close my eyes and swing and see what happens."
Both teams played in Philadelphia until 1954 when the A's moved to Kansas City. They have met six times in interleague series. Oakland leads the series 9-7.
The Phillies (57-90) have to win at least six of their last 15 games to avoid their first 100-loss season since 1961.
ATHLETICS: OF Khris Davis remained on paternity leave.
PHILLIES: C Andrew Knapp started for the first time since coming off the disabled list following a hand injury.
ATHLETICS: RHP Kendell Graveman (5-4, 4.48 ERA) makes his seventh career interleague start and first vs. Philadelphia. Graveman has pitched well since Aug. 8, going 3-1 with a 3.92 ERA and the bullpen has blown leads in his three no-decisions in that span.
PHILLIES: RHP Ben Lively (3-6, 3.86) tries to continue his push to be in the 2018 starting rotation. He has a 2.57 ERA in his last three starts.