For 50 minutes today, the Redskins outplayed one of the elite teams in the National Football League. Then, as Coach Joe Gibbs said, they collapsed in the final 10, turning a close game into their fourth straight defeat with five blatant errors.

Following the 36-13 loss to Philadelphia, Gibbs severely criticized his players. He said that they "came out and played hard and when something bad happened (in the fourth period), when they had some adversity, things came apart at the seams.

"When we have to have something, we don't seem to be able to get it. We just collapsed. That's the best way of putting it."

The Redskins, off to their worst start since 1965, were trailing, 14-13, when the self-destruction began. A 43-yard kickoff return to midfield by Wally Henry, who was allowed to get outside the defensive containment, was the first blunder. Philadelphia turned that mistake into a quick touchdown, then used an interception, a safety and two fumbles to score 15 more points in the final 6 1/2 minutes.

The Redskins also failed to capitalize on a fine offensive performance in the opening half, when they outgained Philadelphia by 210 yards (the Eagles managed only 55) and held the ball for almost 12 more minutes. Yet Washington trailed, 7-6, at intermission.

"I've been on teams that have lost four in a row before," said tackle George Starke, who missed all but three plays with a broken right hand. "But I've never been involved in anything like this. Those other times, the players at least had won before; they had something to fall back on, they knew eventually they were good enough to win.

"But these people haven't won yet, they don't have a background of success to fall back on. That's what makes it such a very, very difficult situation."

The Redskins seem to be improving in some areas weekly, yet still haven't come close to winning because they can't avoid errors at the worst possible times. Other than a 30-point output last week against St. Louis, Washington hasn't been able to score consistently, despite some impressive offensive efforts.

Worse, more Redskins are getting injured. Beside losing Starke early in the first quarter, Washington played the second half without fullback Wilbur Jackson (knee sprain), who had gained 64 tough yards against one of the NFL's best defenses. Mark Moseley, who made two of four field goal tries before intermission, aggravated a leg muscle pull on the third-quarter kickoff.

All three may be able to play next week against San Francisco in RFK Stadium. But Gibbs said the injuries are "destroying our continuity. You look around and someone else comes off the field. George gets hurt and Joe Jacoby goes from guard to tackle the whole game and Ron Saul has to play guard after just coming off the injury list. That line had never practiced together. Wilbur's playing good and he goes down, too.

"We're awful thin already. And to lose more people, we just can't keep making up for things like that."

Philadelphia, winning its opening four games for the first time since 1954, realized how much the game turned on the Redskins' opening-half scoring problems. Even with an improved performance over the last two quarters, the Eagles were outgained by 116 yards, the third straight week the Redskins have lost despite the larger total offense.

"I feel fortunate to win after the way we played in the first half in contrast to the way they played," Coach Dick Vermeil said.

After punting on their opening possession, the Redskins drove to the Eagle 20, eight, two and five, yet came away only with two field goals.

They had a seven-yard touchdown pass from Joe Theismann to Art Monk nullified when they took more than 30 seconds to get off the play. They were hurried into trying a field goal with two seconds left in the half and the ball at the Philadelphia five when they couldn't stop the clock after using up all three of their timeouts earlier in the half.

One unnecessary timeout was called when Starke got hurt, another came on a formation mixup and a third was called when Gibbs couldn't decide whether to kick a field goal or go for a touchdown on a fourth and two with four minutes remaining.

"We gave this game to them," Monk said. "We've got to score more. We can't keep getting so close and coming away with nothing."

The Redskins' game plan kept Philadelphia off-balance the entire first half. Theismann, who threw for 265 yards, completed 16 of 23 passes for 193 yards in the first 30 minutes, usually finding wide-open targets. Halfback Terry Metcalf had seven catches for 113 yards, and Gibbs' two-tight-end offense opened good holes for Jackson, neutralizing much of Philadelphia's pass rush.

Yet a 13-yard screen pass to Louie Giammona in the second quarter, set up by an interference call at the Redskin 20 on Jeris White, was enough for Philadelphia to offset all that offense and take a 7-6 lead into the third period.

The Eagles, who had run only 17 plays in the first half, took the second-half kickoff and used 15 plays to move 72 yards for another touchdown by Giammona, on a one-yard dive. Giammona was playing for the injured Wilbert Montgomery.

A 25-yard pass from Theismann to tight end Don Warren off a scramble got the Redskins untracked early in the fourth. From a first down at the Eagle 13, John Riggins, who had replaced Jackson, gained nine yards off left guard. Two plays later, Riggins bulled into the end zone behind blocks by Otis Wonsley and Mark May. Moseley converted and Washington trailed, 14-13.

And then the Redskins fell apart. The special teams, which had struggled against St. Louis last week, broke down again on the ensuing kickoff. Henry broke outside and gave the Eagles excellent field position at the Philadelphia 49.

"That return picked up the tempo, it got us rolling," Giammona said.

The Eagles quickly were ahead, 21-13, when receiver Charles Smith ran a fine pattern on cornerback Lemar Parrish and broke free for a 29-yard touchdown pass from Ron Jaworski.

After the kickoff, Theismann tried a swing pass to Riggins which the Redskins said was tipped by end Claude Humphrey. Riggins tried to catch it but the pass bounded off his hands and into the arms of linebacker Reggie Wilkes, who ran to the Washington 12. Tony Franklin eventually kicked a 28-yard field goal.

The Redskins were penalized for clipping on the next kickoff. On first down from the their 10, middle guard Ken Clarke broke free and grabbed Theismann in the end zone for a safety as the Redskin quarterback tried to roll left before passing.

After Joe Lavender intercepted a pass from Jaworski and returned it to the Redskin 38, Metcalf bobbled a handoff from Theismann and fumbled, the Eagles recovering at the Washington 30. That turnover led to Franklin's 36-yard field goal and a 29-13 advantage.

Gibbs decided Theismann had enough, and sent in rookie Tom Flick "to give him a taste of what it's like playing." Flick soon found out: he was clobbered on a blitz by Wilkes and Al Chesley and fumbled. Defensive end Greg Brown, from H.D. Woodson High School in Washington, picked it up on the seven and scored, giving Philadelphia 22 points in six minutes.

"Everything we say sounds like an excuse, if you talk about injuries and those things," Theismann said. "It's just up to us to get as mad as we can and stop talking about it and do somethng about it.

"We're better than we are showing. I'm sure of that. We just have to play for four quarters and forget all these mistakes. That day will come, I'm sure of it."