The Annandale Boys Club, under investigation by Fairfax County authorities, grossed $305,964 from its five-night-a-week bingo operation in 1976, according to a report received by the county yesterday.

The club paid $87,858 of that to Landlord Investments, Inc., for rent, maintenance and other expenses connected with the use of its Baileys Crossroads bingo hall, and cleared $84,226 for use in the club's youth sports programs, the report said.

According to the report, $23,518 from bingo was turned over to the club's general account, $42,455 was put in a building fund, $14,252 was placed in a scholarship fund and $4,000 went into a bus fund.

The $305,964 gross does not include about $2,000 paid in prizes each night - about $500,000 a year - so the total cash handled by the club's bingo operation would have been about $800,000.

Fairfax Commonwealth Attorney Robert F. Horan Jr. has said that investigators have found evidence of illegal payments to workers at the club's bingo games and that the lease agreement is under scrutiny.

Under the 1973 law that made bingo the state's only legal form of gambling, games must be sponsored by nonprofit organizations; workers must be members of the sponsoring organization, and no member of the organization may profit from the bingo proceeds.

The $87,858 paid to Landlord Investments, an average of $7,320 a month, includes "rent, electric, air-conditioner, janitorial supplies, custodial services, trash collection, maintenance repairs and remodeling," according to the club's report, signed by treasurer Marion Reading.

Landlord Investments, a corporation formed by Edward L. Hinkle and Robert Gerber, leases the hall from the Row Corporation for $2,000 a month, including utilities, according to officials of the corporation that owns the bingo hall.

Other expenses included $78,383 in bingo prizes and $27,268 for bingo supplies.

The Annandale Boys Club bingo game grossed an average of $25,500 a month last year compared to $27,600 a month during operations in 1975, according to the club's own figures.

The biggest bingo game in Northern Virginia, based on the annual reports that must be filed in each county, was conducted by the Montessori School of Alexandria. That game grossed $477,317 in 1976, and counting the $2,000 paid out in nightly prize money, the Montessori game would have handled nearly $1 million.

The Montessori game transferred $132,095 to the school's account and donated $16,333 to charities. It paid out $131,263 in prizes and spent $35,771 on bingo supplies. Montessori paid $55,027 for rent; $17,491 for repairs and maintenance; $11,613 for electricity, and $7,440 for janitorial service.

The Montessori School cut back games to three nights a week in October, allowing other nonprofit groups to use the facility the other nights.

A third large bingo operation, sponsored by Odd Fellows Lodge 38 of Alexandria, grossed $192,003 in 1976, but made only $7,697 in five months of operations.

Its Bingo game is held in a hall leased by Robert Gerber, president of Gerber Enterprises, to whom the lodge pays $3,500 a month.