About 200 McLean area residents were admitted into the Central Intelligence Agency's nearby barbed-wire-enclosed headquarters last night--the first large public meeting ever held inside the CIA--to protest traffic problems they foresee with the agency's planned expansion.

After complaints that the federal government is treating the George Washington Memorial Parkway as "a sacred cow," spokesmen for the CIA and the National Park Service agreed to study putting more CIA traffic on the parkway, owned by the government.

Rep. Frank R. Wolf (R-Va.), who helped arrange last night's meeting, said, "There is an obligation for federal roads to bear a greater share of the federal traffic if they can."

CIA and Virginia highway planners also promised to permit citizens to participate in the traffic study that will begin this summer in conjunction with the CIA expansion. It will study traffic conditions on Dolley Madison Boulevard (Rte. 123), the main entrance to the agency; on the parkway, now a minor entrance; and on Georgetown Pike (Rte. 193), where a gate is open for employes only during rush hour.

The expansion, scheduled to begin next spring, is expected to take three years and to cost more than $100 million and will bring 3,000 CIA employes to McLean from offices now scattered around Washington. The CIA already has agreed to add no more than 1,000 new parking spaces to the 5,000 it already has at its headquarters, thus forcing greater employe car pooling in 1987.

Most of the more than two dozen speakers thanked the CIA for holding the meeting, many admitting they had come in part out of curiosity to see the 20-year-old headquarters of the secret intelligence agency. But all expressed concern about the traffic it already generates on local Fairfax County roads and the future traffic the expansion will bring.

The National Capital Planning Commission, the federal planning agency for the Washington region, gave preliminary approval to the CIA expansion last year but still must approve traffic changes to entrances on Rtes. 123 and 193 and the parkway.