A group of federal workers who quit the Blue Cross/Blue Shield medical insurance plans within the past two years filed suit yesterday asking for a share of the $600 million in refunds that the company recently announced for current enrollees.

The suit, filed in U.S. District Court in Washington, seeks an injunction barring the first distribution of refunds, which range up to $400, until the proper share of those who left the plans can be determined.

According to Blue Cross/Blue Shield, the refunds are being made because the premiums charged for 1983 and 1984, set on the basis of anticipated costs, brought in more revenue than was needed. However, the company said it was distributing the refunds only to those enrolled on May 1 because "it would be too difficult to track down those who left" the programs.

Under a plan approved by the federal Office of Personnel Management, the first refunds are scheduled to be made in October. But the suit says the plan amounts to "unjust enrichment" of current enrollees because it does not compensate all those who subscribed in 1983 and 1984.

The number of federal workers enrolled in Blue Cross/Blue Shield has dropped from about 1.5 million nationwide in 1983 to 1.4 million this year, but the suit does not indicate how many former enrollees might be eligible for refunds.

The lead plaintiff in the class action suit is Ethel Bolden of Northwest Washington, an employe of the General Services Administration.