ASHBURN, Va. - In less than a month, the mood needle on the Washington Redskins has swung from overwhelmed to overjoyed.

Whether it’s coach Jim Zorn leading cheers of “Hip, Hip, Hooray!” in the locker room or the usual pandemonium that follows any victory over the team the fans love to hate, the supposed bottom-feeders of the potent NFC East have made it known they intend to be a player when postseason berths are on the line in December.

“We’re not pulling up the rear,” receiver Antwaan Randle El said Monday. “We’re in the mix.”

No argument there, not after a 26-24 upset over the double-digit favorite Dallas Cowboys in the Redskins’ final regular-season game at Texas Stadium. After a dreadful opener against the New York Giants, Washington (3-1) has won three straight heading into another showdown Sunday against the Philadelphia Eagles — a game that, thanks to the oddball schedule, will be the last divisional road trip of the season.

“It was a game that helped keep the NFC East even, if you will,” said Zorn, the first Redskins coach to win at Dallas on his initial try since George Allen in 1971. “All four teams are solid teams, and it’s still anybody’s division. Our goals are still ahead of us, and we made that so by beating Dallas in Dallas.”

Linebacker London Fletcher arrived home late Sunday to find that a neighbor posted a sign on his door celebrating the victory. She told him watching the game on television almost moved her to tears.

“Beating Dallas,” Fletcher said, “is a lot different from beating somebody else.”

Fletcher apparently dressed in a hurry Monday morning, however. He dared show up at Redskins Park wearing two shades of blue, a fashion faux pas that escaped his attention until someone pointed it out as he stood before the cameras.

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“Dallas colors, huh?” he said, pulling his shirt up to his chin. “I got to take this shirt off.”

Fletcher then addressed the issue of the day. Given that everyone in the organization — Zorn included — had warned it would take a while for the team to get rolling under a new coach, how it is that things have clicked so quickly?

“Maybe people underestimated our resolve,” Fletcher said. “And just how battle-tested we were from last year, how it carried into this year. We knew we had a good football team last year. We let some games get away from us and we were fortunate to get into the playoffs. But this year we’re finishing better.”

They seem to be doing everything better. The Redskins have yet to commit an offensive turnover — the one on their stat sheet came on special teams in Week 2 — which means opponents have started 28 straight drives and 42 of 43 in their own territory. Every quarterback in the league with at least 20 pass attempts this season has thrown an interception except for Jason Campbell.

Clinton Portis (369) and Santana Moss (421) are in the top five in yards rushing and receiving, respectively. Rookie Chris Horton, who has taken the starting strong safety job from Reed Doughty, already has four takeaways (three interceptions, one fumble recovery).

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The defense turned the Cowboys into a one-dimensional team. Marion Barber carried only eight times for 26 yards. Terrell Owens, contained by Shawn Springs and then Carlos Rogers, caught only seven of the 17 passes thrown his way and averaged barely 10 yards per reception.

“We’ve earned a little respect,” cornerback Fred Smoot said. “But we’ve got another NFC East game this weekend that we’ve got to win. We ain’t going to jump the gun.”

Zorn, who has shown himself to be a perpetual energy machine, almost looks corny at times as he enjoys the ride. The “Hip, Hip, Hooray!” bit during the post-game celebration came from Chuck Knox, his Seattle Seahawks coach in the early 1980s.

“It’s very old school,” Zorn said. “’Hip, Hip, Hooray?’ C’mon. But it kind of fired me up. When I was a player, I thought to myself when we were doing this, ’What’s wrong with old school?’ ... It’s kind of a special cheer for special games, in my mind.”

For all the excitement, however, Zorn still won’t give ground when comparing the Redskins-Cowboys rivalries with the Raiders-Seahawks games of his playing days, even though he’s caught a lot of grief about it.

“I never heard about the Seattle-Raider rivalry,” Fletcher said with a sad shake of his head. “I told him this is different.”

Said Zorn: “I didn’t have a sense of hate or anything. I didn’t have a secret T-shirt on underneath saying ’Beat Dallas!’ or anything like that.”

How about a “Beat Oakland” T-shirt. Got one of those?

“Yeah,” Zorn said. “’Raider Busters.’ Absolutely.”