With development in downtown Bethesda already bulging at the seams, Montgomery County officials are taking an unprecedented step to join forces with a developer to build a multimillion-dollar complex near the Bethesda Metro Center.

The project, known as the Bethesda Metro Development Project, will consist of a 1,000-car underground public parking garage that will be capped by a 200-unit residential high-rise building.

Under county plans, a strip of stores, including the McDonald's Raw Bar, will be razed to make room for the development, which is slated for a 2.3-acre tract bordered by Old Georgetown Road, Woodmont Avenue and Edgemoor Lane. The county bought the land three years ago.

"We're very excited about this project. We feel it's going to work," said Thomas Huff, special assistant to the director of Montgomery's Department of Transportation, which is overseeing the project.

"It's the first venture for the county," Huff added. "It's unusual for us to put out like this, but we feel it's a coming thing, with a scarcity of land."

Huff said that Montgomery may embark on similar joint-venture partnerships in other high-density areas, such as Silver Spring, where several developers already have indicated interest in such projects.

While nearly 85 firms had requested detailed information about the Bethesda development plan in the past several weeks, only three submitted site proposals as of Wednesday, the county's cutoff date to submit plans.

The three firms are: Caldwell American Investments Inc. of Troy, Mich.; Carley Capital Group of the District; and Forest City Dillon Inc. of Cleveland.

Selection of a developer is expected to be made by Sept. 1, Huff said. Upon selection, the county will act as partner in the construction of the parking garage and two pedestrian bridges -- one to the nearby Metro Plaza and the other over Old Georgetown Road to the future Bethesda Place office-and-residential development.

The entire project is expected to be finished by June 1988.

Huff said that the residential units probably will consist of rental apartments, but said that some condominiums also may be built. Limited office and retail space will be available as well, he said.

In accordance with a county law aimed at increasing affordable housing, 12 1/2 percent of the units will be moderately priced dwellings.

Transportation officials declined to place an overall price tag on the project, but estimated that the cost of the garage would be about $23 million. That figure includes the $7 million the county paid for the site in 1982.

The estimated cost of $10,000 per parking space compares with the $6,000 per space the county usually pays. Costs are higher partly because the garage will be underground.

The garage will be subsidized through Montgomery's Bethesda Parking Lot District Enterprise Fund, which generates money from other county-run parking lots and from developers who do not build parking sufficient for their own needs.

Huff said the county has hired the Annapolis-based consulting firm of Zuchelli, Hunter & Associates, Inc., for technical assistance in evaluating the site proposals.