It was gray and rainy, and nobody knew if the teams were good or bad. The vendors had scant supplies of the new league's pennants, and the hulking gate-keepers were inspecting bags and coolers for hidden cans of beer.

But by 2:30 p.m. yesterday, enthusiastic crowds were thronging into R.F.K. Stadium to see the first game of new Washington Federals. They came because they were curious, they said, because they never were able to get tickets to Redskins games and because they were plain old football freaks.

And football, after all, is football, no matter what the team.

A half hour before kickoff, a group of 37 from Prince George's County, many wearing Redskins caps, ended its three-hour tail-gate party and marched into the stadium singing "Hail to the Redskins." Ronnie Pickerel, the declared ringleader, said they had bought a box for the season, at $162 each--and pooled another $412 for the party.

"We all party together, and we're all football fans," was the nearest Pickerel could come to an explanation. "We're going to root the Federals to victory."

Fellow partier Anne Swank of Greenbelt said she was delighted that a new team had come to the city. "I don't have Redskins tickets; that's the real reason I'm saying that. It's the generation before ours that's got the tickets."

Football fanatic Lorenzo Crowe, a dapper gentleman from Northeast Washington, said he was coming to the game but refused to buy season tickets until he had seen the team play at least once. "I've been a Redskins fan since the beginning of time," he said. "I just want to take a look at this."

Four Fairfax men arriving together said they had low expectations. The players, one man said, were "fools" to play in the new league. "My mother could play in this league," another added contemptuously. But they were there, part of a crowd of more than 38,000 that watched the Federals lose to the Chicago Blitz, 28-7.

Eight former fraternity brothers from the University of Maryland arrived together. They were not football freaks or Federals fans. They just wanted to see what the team was like.

"This is a piece of history," said Jordon Spector of Silver Spring. "Next year, it probably won't be here. I don't think this is going to last."

His friend, Ron Young, saw greater possibilities, however. "It will be great in the spring, sitting with a beer on the sunny side of the stadium."

Even the vendors were waiting to see what was happening.

"I'm just seeing what the crowd is like," said Irving Millard, who was selling only Redskins buttons. "Who knows who the Federals are? Nobody. But 90 percent of the people here are Redskins fans."

Clarence Gale, who had a large stand near the stadium entrance, was selling Federals pennants--green, black and white, the team colors--for $3 and Redskins pennants for $5. "My Lord, all the stuff from the Superbowl is still selling," he said. "They're still collectors items."

Eugene Wilson, on his way to work as a clerk at Hadley Memorial Hospital, said all his friends were watching the game on television and that the new league may be better than the N.F.L. "These are guys who are hungry to play. They want to play the game, and don't want to go out on strike," he said.

"It's probably going to break up a lot of marriages, though," Wilson added. "Wives get enough of it already. It's going to be real interesting."