Over an elegant dinner at Dominique Restaurant last fall, Dr. Robert G. Rosenberg, the executive director of Group Health Association, told the leaders of GHA's doctors union that the world had changed for Washington's oldest and best-known health plan.

Group Health -- a 145,000-member nonprofit group founded in 1937 as an anti-establishment cooperative -- would be forced to take a harder line at the bargaining table with its 160 unionized doctors, he said. Rosenberg would no longer negotiate directly with the union, he told them, but rather had hired a veteran corporate labor lawyer to deal with the Capital Alliance of Physicians.

The stage was set for what followed: a bitter 25-day doctors' strike that ended yesterday after a lengthy conflict. The strike illustrates the intense economic pressures facing health-care providers and highlights new issues facing doctors who increasingly find themselves in the role of employes working for corporations rather than for themselves in private practice.

GHA doctors -- along with those at D.C. General Hospital and other city government agencies -- are among an estimated 10,000 to 20,000 physicians nationwide who belong to labor unions, a small but growing response to concerns over wages and working conditions in a health-care industry whose skyrocketing costs have prompted an intense movement to control costs.

"Whether GHA management are good guys or bad guys doesn't really matter," said Dr. Jonathan House, a New York internist who founded the National Federation of House Staff Organizations, the largest doctors labor organization. "They have to operate in the marketplace . . . . And the nonprofit behaves more and more like the for-profit."

"We have bent over backwards, and we couldn't always keep doing that," Rosenberg said in an interview. GHA had historically been "soft, very prolabor, very liberal and very consumer oriented," and while those values still exist, he said, "It is really a question of whether GHA can survive in a rapidly changing competitive environment."

GHA had only four competing health maintenance organizations in 1983, but expects as many as 15 area HMOs by next year -- including several whose costs are 10 percent or more below GHA's, he said.

The key issue for GHA became doctors' productivity, specifically the question of who decides exactly how doctors spend their time, according to GHA officials.

The officials said yesterday the new contract gave management part of its desired changes. Doctors will be required to devote several more hours within their 35-hour minimum workweek specifically for office visits.

Also, GHA will begin shaping a controversial "incentive" pay system designed to reward doctors for treating more patients, a move the union strongly decried as the beginning of "assembly-line medicine."

Under the new contract, GHA will be able to respond to patient demand by scheduling doctors for more evening and Saturday appointments, said Harold Wool, the elected president of the member-owned GHA board of trustees.

"Shorter waiting time and increased access to doctors" should result, Wool said. GHA is to resume full operation today at its seven Washington area centers -- one in the District, three in Maryland and three in Virginia -- with a backlog of some 5,000 postponed appointments with doctors.

The doctors union is "happy with the settlement" because the two sides agreed that a joint labor-management committee and an arbitrator -- rather than GHA alone -- will draft the new standards to determine numbers of patients to be treated for each medical specialty, said Dr. Nieves Zaldivar, a GHA pediatrician and the union president.

"The basic issue was that [GHA management] wanted to change the way of life" by increasing productivity standards, said Abraham Zwerdling, the union lawyer, who described GHA doctors as "sincere, dedicated professionals who came to practice quality medicine and didn't want to hustle patients."

"We have to operate Group Health to generate a positive bottom line, to replace our equipment, to modernize, and to market ourselves at a competitive premium," said Rosenberg, who denied that the new system would result in a speedup of patient consultations.

GHA doctors earn an average of $91,000 a year, and will receive 5 percent raises over three years, plus the bonus pay of up to 3 percent a year if GHA implements the incentive system.

"This was a very unusual negotiation," said Emmett DeDeyn, the veteran federal mediator who supervised bargaining for the Federal Mediation and Conciliation Service.

The doctors, DeDeyn said, "were more humanitarian than interested in money. They want a decent life style appropriate to a physician, but their predominant concern was not financial status. It was patient care . . . . It was unusual to find people who were not just interested in their own self-interest and gain. That is unusual at the bargaining table." He said GHA management shared the concern for the quality of care, "but their approaches were different."