Bill Sprouse was frustrated.

Visiting from Eustis, Fla., Sprouse drove his van with seven passengers into Washington a few days ago to visit the Capitol. He drove and drove and drove around looking for a parking space. He couldn't find a legal one.

Like thousands of tourists and other visitors to Capitol Hill. Sprouse was a victim of the generosity of Congress to itself and its staff. All 8,494 parking spaces in the 181 acres that make up the Capitol grounds are reserved for free parking by people who work on Capitol Hill.

Yesterday the Senate defeated, by a vote of 65 to 28, an attempt by Sen. Gary Hart (D-Colo.) to climinate the free parking and to set apart some spaces for visitors to Capitol Hill, such as Sprouse.

Hart contended that the free parking amounts to a $7 million annual subsidy by the nation's taxpayers to congressional workers, asking Capitol Hill one of the most costly - and surely among the most prestigious - parking areas in the country.

By rough count, there is one parking space on Capitol Hill for each two congressional employees, a ratio far more generous than that provided for the government's executive agencies elsewhere in the city.

In the rest of downtown Washington, there is only one government-owned parking space for every seven federal employees, according to the National Capital Planning Commission. Moreover, many of the workers are required to form car pools to qualify for parking spaces, and fees are charged in many garages and lots.

The main reason cited on Capitol Hill for the congressional liberality with itself is irregular hours.

Members of Congress, their office employees and committee staffs say they cannot be bound by the typical 9-to-4:30 hour of the bureaucracy downtown, and they contend mass transit is inadequate.

To provide space for Capitol Hill workers, public parking in banned in an area that stretches from Union Station on the north to D Street on the south, and from 1st Street NW-SW to 2rd Street NE-SE on the east.

Within this area are six congressional garages (plus two small ones for the Supreme Court and the Library of Congress, a dozen open-air lots (many occupying land formerly used as parks) and nearly 2,000 curbside spaces poted for "parking by permit only." The Capitol plaza, where presidents are inaugurated every four years, also serves as a parking lot for 343 cars.

Yet, judging by interviews with congressional staff officials and some lawmakers, the supply of parking spaces in considered inadequate.

Several weeks ago, the House Administration committee - the housekeeping unit of the House of Representatives - sought to expand its parking facilities by paving over the congressionally owned site of the now-demolished Providence Hospital at 2d and D Streets SE. This would have provided 400 spaces.

Neighborhood residents mounted such an intense lobbying effort against the proposal that it was dropped.

Rep. Frank Thompson Jr. (D-N.J.), the committee chairman, said in announcing the reversal that he is constantly badgered by fellow congressmen and staff members with requests for more parking.

One problem, Thompson said, is that permits - other than those for reserved spots in garages - are greatly overissued, making them mere hunting licenses for scarce spaces in lots or at curbside.

As a result, employees must park in nearby residential neighborhoods.

Soon, however, the city government plans to restrict all-day parking in those neighborhoods to residents only, putting a further squeeze on Hill workers. Similar all-day parking bans already are in effect in scattered sections of the city that once were invaded by commuters' cars.

Hart, in pushing his proposal yesterday to climinate congressional free parking, said it would "show the American people we are serious," about solving problems of energy and air pollution by encouraging commuters to shift to car pools and mass transit.

Sen. Walter Huddleston (D-Ky.), chairman of the Legislative Branch Appropriations Subcommittee, who was managing the bill Hart was seeking to amend, opposed the proposal. He said all federal employees everywhere should be treated alike, and that congressional staffs should not be singled out for paying fees.

Sen. Harry F. Byrd Jr. (Ind.-Va.) was the only Washington area senator who sided with Hart. Sens. Paul S. Sarbanes (D-Md.) and William L. Scott (R-Va.) opposed Hart's proposal. Sen. Charles McC. Mathias Jr. (R-Md.) was absent.

Officials say relatively few congressional workers now use transit or car pools to get to work.

F. Nordy Hoffman, the Senate sergeant at arms who oversees Senate parking, had a poll taken last year of commuting habits. It showed that 79 per cent of the Senate employees who responded drove their cars, with a scant 3 per cent using mass transit. The poll showed a clear preference for rail transit over buses.

"The trouble now," one congressional employee noted, "is that Metro doesn't go anywhere yet, as far as getting to where people live."

A major problem, cited in both the House and Senate, is that Congress is composed of 539 separate members' offices, 37 standing committees and several related offices, all of which set their working hours and make such solutons as car pools difficult.

Each office arranges distribution of parking permits among its employees.

"There is no single objective standard under which parking permits are distributed," said one knowledgeable House aide. Seniority and individual need are most commonly taken into account.

In the House, where all members are permitted to hire up to 18 staff members (some work in members' districts back home), each member has one permit for himself and may distribute five permits among employees.

Allocations among Senate office staffs vary because staff sixes are based on the population of an individual senator's state.

Still more permits go to committee staff members and other Hill workers, including those who work for the Architect of the Capitol (who is in charge of maintenance) and in congressional restaurants and supply rooms.

There are 181 spaces set aside for news media, including 64 for daily newspaper and wire service correspondents. Four permits have been issued to reporters for The Washington Post who are regularly assigned to the Capitol.

Recently, a subcommittee of the National Press Club pondered the ethics of reporters accepting free parking at the Capitol, but reached no conclusion, according to Sam Hana, subcommittee chairman and correspondent for the New Orleans States-Item.

Hanna said the near-total lack of commercial parking on Capitol Hill was one reason, along with the irregular hours and the fact that no mechanism exists by which reporters or others can pay for Hill parking.