Physicians serving the 112,000-member Group Health Association voted late yesterday to accept the major points of a new three-year contract with the organization, averting for at least 24 hours a strike that had been threatened for midnight last night.

If approved today by the health maintenance organization's board of directors, the pact will raise the average GHA physician's salary from $58,500 to $71,658 in 6, 7 and 8 percent steps.

Betty Payne, spokeswoman for GHA management, said yesterday evening that executive director Edward Hinman is "optimistic we'll have a final settlement [today]. It looks satisfactory from our point of view, but you know the board."

Two years ago, after a similar ratification vote by the physicians' union, the board rejected a settlement proposal during an 11-day doctors' strike against GHA -- the only such strike in American medical history by fully trained physicians.

The pact approved yesterday by the doctors, 71 to 9, is not complete but covers the major issues. The areas yet to be settled are mere "clerking" chores, according to Dr. Norman Lieberman, president of the physicians' union.

Lieberman called the contract "hard," but said his bargaining team did not think it could do better. "It becomes a question of how much blood you can get out of the stone," said Lieberman. "I think we drained it dry."

The Group Health Association is a nonprofit prepaid health care organization that receives an annual fee from members who are provided with all their health care needs, including hospitalization. The cost, similar to that of a conventional insurance plan, is independent of the frequency of members' visits to physicians.

The unionized physicians were defeated this year, as they were two years ago, in their quest for the right to establish outside private practices. y

The GHA board has maintained that, as a matter of principle, organization physicians may not see outside patients.

The physicians will also be required to care for a larger volume of patients than currently, which the doctors had tried to avoid.