Congressional Quarterly, the news research organization that reports on Congress, on Jan. 2 will become the first known Washington-area firm to subsidize Metrobus and subway fares for its employes.

The firm, which has 125 employes, will join more than 100 major companies in dozens of cities -- including Los Angeles, Dallas, Chicago, Seattle, Hartford, Kansas City and Minneapolis -- that already are paying part or all of their employes' bus fares.

The subsidies are designed to conserve gasoline, support mass transit and help reduce city air pollution.

Spokesmen for several large Washington companies said yesterday that they had not previously considered offering mass transit subsidies to their employes but would consider it now.

Richard Brown, a vice president of Riggs National Bank, Washington's largest bank with more than two dozen branches and 1,800 employes, said, "We used to give street car passes and still give bus tokens for employes on downtown business trips and I think we would definitely consider this." Spokesman for Garfinckel's and Perpetual Federal Savings and Loan also said their firms would consider such subsidies.

"This (Congressional Quarterly) is the first Washington company I've heard of" that will subsidize the use of public transit, said Metro spokesman Cody Pfanstiehl. "And I say hooray for them."

The CQ subsidy was hailed by the Metropolitan Washington Council of Governments as "a precedent we heartily endorse for Washington," said Ron Sarro, assistant director of transportation.

Congressional Quarterly, with offices at 22rd and P streets NW, plans to pay "Probably 20-to-25 percent" of bus and subway fares for the 60 to 70 percent of its employes who commute on Metro, according to John Angier, the company's comptroller.

The idea for supporting Metro with company-subsidized bus and subway fare comes from the quarterly's parent publishing firm, the St. Petersburg Times, Angier said. The Times offers its Florida employes free bus tickets and free parking for car pools, Angier said.

"Here at CQ we feel we have a national obligation to conserve gasoline and a community obligation to support Metro public transportation," Angier said.

Details of CQ's Metro subsidy plan are still being worked out but "we will probably buy tokens, farecards or flash passes and then resell them to empolyes at a discount," Angier said. Flash passes, good for two weeks of unlimited Metro bus and subway use, can save commuters "at least $8.25 over regular fares, and more for long-distance commuters," a Metro spokesman said.

For years, car travel and especially parking for commuters has been subsidized by both private firms and the federal government.

Until Nov. 1 an estimated 27,000 parking places were reserved for free or at cut-rate prices for federal employes in downtown Washington, Rosslyn and at the Pentagon.

On that date, an order signed by President Carter required the federal employes to pay a fee deermined by the General Services Administration, about half the going rate at nearby commercial lots.

This fee ranges from $22.50 to $40 a month now. Beginning Oct. 1, 1981, the employes will have to pay the full commercial rate, estimated to be as much as $80 to $90 a month by then.

Members of Congress and their aides, however, still have more than 8,000 free-parking spaces on the Hill that are unaffected by Carter's order. That status is under attack by Sen. Charles H. Percy (R-Ill.). who earlier this month introduced legislation that would require the members of Congress and their staffs to pay for their parking spaces.

The support of public transit by private business began during the Arab oil embago in 1973-74 and surged this year when gasoline shortages appeared again around the country, according to the American Public Transit Association, trade organization for the nation's bus and subway operations.

"Seattle is considered the leader in this," said Ron Hartman, the association's director of planning. "They've now got more than 50 firms giving bus discounts or even free bus tickets to over 10,000 employes."