When Federals owner Berl Bernhard discovered 15 minutes before kickoff last week in Chicago that starting quarterback Mike Hohensee was ill and would not play, his face went blank with frustration. The 31-3 beating that followed was not a total surprise.

When the Federals take the field against the Oakland Invaders here tonight (11 p.m. EST, WMAL-630), Bernhard will be in Florida on vacation. Coach Ray Jauch and his embattled 1-9 team will be enjoying no such respite. And, although Hohensee is scheduled to start, the evening in no way promises to be soothing.

The Invaders have a 4-6 record, but they can tie the Pacific Division-leading Los Angeles Express with a victory. So while the Federals are trying to find ways to emerge from a frustrating, fractious six-game losing streak, the Invaders, although they have lost three of their last four games, are motivated by the playoff race.

Jauch has tried to push aside conjecture about his future with the franchise--including reports that Bernhard had sought to replace him with Calvin Hill--preferring, instead, to talk about the team's opponents.

"You have to concentrate, what else can you do?" he said. "Oakland isn't on Philadelphia or Chicago's level, but they play a good, balanced offense."

Oakland quarterback Fred Besana is the USFL's second-leading passer, having completed 198 of 319 attempts for 2,405 yards and 11 touchdowns. Besana's career so far has taken on the sort of outstanding proportions that the new league said would be commonplace.

The Buffalo Bills drafted Besana in 1977 out of the University of California, but after three years of trying to find a place with the Bills and Giants, Besana's NFL career came to an end. At 29, he is essentially a rookie.

Besana's primary receiver is tight end Raymond Chester, a 13-year NFL player with the Raiders and Colts. At 34, Chester has caught 45 passes for 617 yards. Another former Raider who has helped the Invaders immensely has been running back Arthur Whittington, whose 709 yards rushing puts him third in the league behind Philadelphia's Kelvin Bryant and New Jersey's Herschel Walker.

Like the Federals, with Coy Bacon, the Invaders' defensive line is buoyed by an aging end, 13-year veteran Cedrick Hardman, who also is an assistant on Coach John Ralston's staff. Hardman played with 1980 Super Bowl champion Oakland.

The rest of the defense has played well, allowing only 16.1 points per game.

With a financial base of 27,000 season tickets, the Invaders appear to rank with the Denver Gold as one of the leading franchises in the league. The departure of the Oakland Raiders for Los Angeles provided the Invaders with a ready-made market.

Invaders owner Tad Taube, who has investments in clothing, computer and electronics firms, said it would not matter to him if Oakland and the NFL's attempts to return the Raiders to Oakland were successful.

"The Denver Gold is not the only show in town. I believe there is a team called the Broncos playing in the fall," said Taube. "They're both doing great. The Tampa Bay Bandits are the second most successful franchise in the league and there's another team called the Buccaneers. The success or failure of the USFL will have nothing to do with teams sharing a city with an NFL team. We can coexist."

There is evidence, however, that the Invaders' attendance is slipping. Oakland's home opener against Arizona drew 41,233, but of last week's 26,989 ticket holders, almost 10,000 stayed home on Mother's Day rather than watch the Invaders play the Bandits.

"I guess the hardest thing about the Raiders that we have to face is that they were winners and fierce competitiors," Taube said. "They leave a legacy that's hard to match."

In a year in which the Redskins won the Super Bowl, that is the sort of legacy and problem the Federals and Berl Bernhard can understand.