Physicians at the Group Health Association voted overwhelmingly last night to authorize a strike as early as tomorrow if the doctors union cannot resolve a contract dispute over workloads with the 140,000-member health maintenance organization.

The 160-member Capital Alliance of Physicians said it would handle only emergencies and hospital cases if the union does not resolve a dispute over "quotas" that the union said GHA is seeking to impose on lengths of patient visits.

GHA, one of the nation's oldest and largest group health plans, is seeking to implement new requirements on the number of patients doctors must see at the association's seven Washington area health centers, according to Dr. Nieves M. Zaldivar, the union president.

The doctors are "very much opposed to a concept of assembly line medicine, in which the time quota allotted by GHA management to a patient may not necessarily conform to the time deemed necessary by the physician" to provide good care, she said in a statement.

GHA's executive director, Dr. Robert Rosenberg, was not available for comment last night.

Doctors voted 88 to 11 at a meeting last night at George Washington University to authorize a strike. Negotiations were to resume early today. The union's three-year contract expires at midnight tonight. The doctors are paid $50,000 to $100,000 a year and generally work 35-hour weeks, according to the union.

GHA, seeking to improve doctors' productivity, is proposing that 5 percent of salaries be withheld but be repaid -- and that a 5 percent bonus be added -- for doctors in various specialties who are able to treat particular numbers of patients, according to union spokesman Henry Fleisher.

The union, one of few physicians unions in the country, struck for 11 days in 1977.

GHA's nurses went on strike for 30 days in 1982 in a dispute over workloads and wages.