Pelfrey pitched his first complete game in nearly three years and Beltran belted a mammoth home run as the Mets handed Haren a rare beating Saturday night in a 6-1 victory over the Los Angeles Angels.
"These days it doesn't happen as often as in the past, but it's fun to go out there and finish what you start," Pelfrey said.
Pelfrey (4-5) entered 0-2 in his previous six outings, though he pitched well in most of those. This time, he gave up five hits in his first win since May 10 at Colorado as the Mets rebounded from a pair of tough losses.
"As a coaching staff we talked today and said this is when you need your No. 1 guy to step up," manager Terry Collins said. "After the last two nights, you need your No. 1 guy to give you a game, and he absolutely did."
The big right-hander struck out five and did not walk a batter for the third consecutive start. He threw a season-high 123 pitches in his third career complete game -- the last one was Aug. 25, 2008, against Houston.
The only blemish was Mark Trumbo's one-out homer in the sixth, and Pelfrey cruised home from there for New York's third complete game of the year.
"He never stayed in one spot. He was good inside, outside. He mixed it around," Angels cleanup batter Bobby Abreu said. "You've got to give credit to the guy. He deserves it."
With the cheering crowd of 31,538 on its feet, Pelfrey retired Vernon Wells on an infield popup to end it. Mets starters have a major league-best 2.46 ERA in 23 games since May 26.
"We didn't get off to the start we wanted, but we've been playing well," Pelfrey said. "I've said we're a lot better than a .500 team and I think by the end of the year it's going to show. We're going to get there."
Haren (6-5) entered with a 2.54 ERA, third-best in the AL, but had trouble holding runners in his shortest start of the season and didn't get much help from his defense. New York stole four bases against him and catcher Hank Conger -- two by Reyes -- while building a 6-0 lead.
"They disrupted my rhythm out there. I was trying to be quick to home, but obviously I wasn't quick enough," Haren said. "The last inning kind of got out of control."
Beltran put the Mets in front with a two-out single in the third, then hit a two-run homer that chased Haren with nobody out in the fifth. Bay also had two hits, including an RBI single, and Reyes scored twice.
"At the end of the last three series, the (opposing) managers have come to me and said, 'Oh my gosh.' They marvel," Collins said about Reyes. "I had one of the managers tell me the other day, 'If he's not the best player in the National League right now, I don't know who is.'"
The Angels, who have thrived during interleague play the past few years, especially on the road, lost for the ninth time in 13 games overall.
Haren gave up seven hits and a season-high six runs in four-plus innings.
"Over the course of the year it's going to happen, even to the best of them," Haren said. "I never really got into a rhythm."
With the Mets already leading 3-0, Reyes drew a leadoff walk in the fifth and stole second.
Justin Turner smacked an RBI single to right and Beltran drove his 10th homer onto the Shea Bridge, a pedestrian walkway above the bullpens that sit beyond the right-center fence.
Estimated at 460 feet, it was one of the longest home runs a Mets player has hit at cavernous Citi Field, which opened in 2009.
"As soon as I hit it, I knew it would be gone," Beltran said. "I didn't really take a look where it landed, but the guys told me about it later."
When he returned to the dugout, a smiling Beltran got an enthusiastic greeting from Reyes, and the Mets were on a roll.
"There's some things that this club has that has kept us afloat," Collins said. "Obviously, one is the play of Jose Reyes. The other is the play and the leadership of Carlos Beltran."
Asked about a report that Scott Boras is interested in representing him, Reyes said there's "no chance" he is changing agents. The star shortstop, who can become a free agent after the season, said he's happy with his current representative, Peter Greenberg. Reyes said Boras went to Colorado to see him earlier this year but they never even had a chance to meet. ... Collins rested Ruben Tejada, saying the 21-year-old second baseman looks a little tired. ... After a big game Friday night that included an outstanding catch, speedy CF Peter Bourjos was on the bench because Angels manager Mike Scioscia wanted Abreu's streaking bat back in the lineup. Abreu, the regular DH, started in LF and Wells was in CF. ... 3B Alberto Callaspo (left hamstring) flied out as a pinch-hitter in the eighth. He should be ready to start when the team begins a three-game series Monday at Florida, Scioscia said. ... Bay has multiple hits in three of his past four games, going 7 for 17 (.412) during that span.