The Washington Redskins have offered a five-year, $300,000 contract to fullback Jim Otis, who played out his option with the St. Louis Cardinals last year.

The Cardinals have until Monday to match the offer, or lose the services of the 6-foot, 225-pound fullback who gained more than 1,000 yards in 1975.

The Redskin offer to Otis, 29, and a nine-year veteran, is low enough so that Washington would not have to compensate the Cardinals with a draft choice. But Larry Wilson, the Cardinals' assistant director of operations, said yesterday, "There is some problem with the Redskin offer, something we're looking into right now. That's all I really want to say about it."

Cardinal owner Bill Bidwill declined to comment, although sources in St. Louis say he is consulting with an attorney about the Redskin offer to Otis and has protested to the NFL.

Terry Bledsoe, assistant executive director for the NFL Management Council, confirmed yesterday, "There are some questions about it, and we hope to resolve the situation in the next 24 hours. Other than that, we'd rather not comment further."

The Redskin offer calls for Otis to receive $80,000 a year in 1978 and 1979, $79,000 in 1980 and $30,000 for each of the final two years of the contract.

That sum averages out to slightly less than $60,000 per year. If Otis were paid $60,000 or more per year, the Redskins would have to give the Cardinals at least a third-round draft choice in 1978. The Redskins do not have a third-round pick to give up.

Ed Garvey, executive director of the NFL Players' Association, said yesterday the Cardinals were complaining because the $30,000 salary the Redskins would pay Otis in 1981 and 1982 falls below the NFL minimum salary of $32,000 for each of those years.

"If they want to file a grievance, that's fine," Garvey said. "But I don't see where they have a grievance because the player has agreed to sign this contract. As far as we're concerned, the Cardinals have until Monday to match the offer. If they don't, Otis would go to the Redskins."

Wilson said the Cardinals have not made a decision on whether to match the offer.

Otis said he preferred not to comment on the situation. "Right now, I don't think it's in my best interest. I'm right in the middle of it. I just know one thing - I want to play football next year; that's my biggest concern.

"I could be happy staying in St. Louis and I could be happy in Washington. I know the Cardinal coaches want me to stay. I don't know how the Redskin coaches feel because I haven't spoken with then. But their offer does indicate they want me to play."

Rick Bennett, a Washington attorney who has represented many Cardinal players, including erry Metcalf, handled Otis' contract talks. He was not available for comment yesterday; nor were Redskin Coach Jack Pardee or General manager Bobby Beahard.

Otis, an All-America at Ohio State, was used sparingly by the Cardinals in 1977, gaining only 334 yards on 99 carries. In his previous seven years, he averaged 3.9 yards a carry. He gained 1,076 yards in 1975, a Cardinal record.

The Redskins have several veteran fullbacks on the roster, including John Riggins, who suffered a knee injury in 1977 and missed the last nine games.

Clarence Harmon, Riggins' replacement, returns, along with veteran Jim Kick and Jeff Kinney, a free agent signed in the fofseason.

The Redskins also made an offer to Houston Oiler detensive back Mike Reinfeldt, but the Oilers have matched it and he will return for his fourth season.