Striking doctors at Group Health Association voted early today to approve a three-year contract to end the 24-day strike that has cost GHA more than $1 million, forced postponement of 5,000 medical appointments and disrupted service at the 145,000-member health maintenance organization.

After a four-hour, closed door meeting, the 160-member Capital Alliance of Physicians, which struck March 3, accepted a compromise agreement by an 80-to-19 vote. The settlement had been approved late last night by the nine-member GHA Board of Trustees.

The new contract is to be signed today at the Federal Mediation and Conciliation Service headquarters and doctors are to return to work Friday at the nine GHA health centers in Maryland, Virginia and the District.

The nonprofit, member-owned GHA said it will begin scheduling makeup appointments for thousands of members who missed appointments during the strike.

Before last night's meeting, Dr. Robert G. Rosenberg, GHA's executive director, said he hoped a settlement would bring "the process of healing" wounds caused by the strike.

The key to the proposed three-year contract settlement is the creation of a joint labor-management committee and neutral arbitrators to resolve two of the most troublesome issues: setting productivity standards for salary bonuses that would be based on the number of patient "encounters" expected of each physician, and deciding whether to reprimand or suspend up to 11 doctors for alleged neglect of duties during the strike.

Sources on both sides had said late yesterday the agreement might be rejected by doctors, primarily because they had strongly opposed the "incentive pay" plan and were angered by GHA's proposed discipline, even though GHA agreed to reduce proposed suspensions from as long as 90 days to 20 days.

"Even a letter of reprimand is considered a serious blow to a professional career," said Abraham L. Zwerdling, a lawyer for the Capital Alliance of Physicians.

The strike, according to both sides, was triggered by GHA's original proposal to increase most doctors' office-visit hours and start paying bonuses up to 5 percent based on the number and severity of cases doctors treated. The union complained that such plans could force a damaging speedup of service and leave them less time for other duties.

The contract sets complicated formulas for figuring minimum office hours in each medical specialty, but Rosenberg said it will assure that doctors increase by one to five hours per week the time devoted to office visits. The doctors, who earn an average of $91,000 a year, will maintain their minimum 35-hour workweek.

Wages, which were not a major issue in the strike, will increase 3 percent this year while the joint committee studies productivity. The committee and an arbitrator, if necessary, will set "reasonable encounter standards . . . ," the contract said. Doctors will then receive up to 3 percent in incentive pay for meeting the targets, in addition to 1 percent annual raises.