The federal government has agreed to pay $4.2 million to 500 former and current employes of the General Accounting Office who charged that they were victims of years of racial and sexual discrimination limiting them to low-paying, "dead-end" jobs.

A formal announcement of the award -- one of the largest ever made in a discrimination case -- is scheduled to be made Monday when lawyers for the U.S. Justice Department and those representing the employes appear before U.S. District Court Judge Louis F. Oberdorfer here.

Black employes affected by the class action suit, filed in 1973 by three GAO employes, could receive between $1,000 and $30,000 each, depending on their length of service, while others can receive up to $10,000 each, according to Kerry A. Scanlon of the Washington Lawyers Committee for Civil Rights Under Law, one of the attorneys in the case.

The wording of a consent order to prohibit future discrimination must still be worked out, according to Marc L. Fleischaker, another lawyer representing the plaintiffs.

Assistant U.S. Attorney Ann DuRoss, who represented the government, could not be reached for comment. Both Fleischaker and Scanlon said DuRoss had told them earlier in the day that the Justice Department agreed to the settlement.

The class action suit charged that a "blatant pattern and practice of discrimination against blacks and women" kept most of them in low-level clerical jobs.

The suit charged that announcements of promotions were not posted, that little or no training was offered to employes seeking technical or professional jobs, that outsiders were hired for the better-paying jobs and that an ineffective equal employment opportunity office did nothing.

"The discrimination was so great here that people were retiring at grades one and two after 20 and 30 years of work and I just felt I had to do something," said Otha J. Miller, 70, one of three employes who filed the suit.

Miller is a classic example of the bias many believe has been long suffered by employes in the predominantly black transportation and claims division of the GAO.

A college graduate with postgraduate credits, he came to the division in 1942, rose to a GS4 in 1946 and remained at that level for 30 years. He was finally promoted to a GS9 in 1971, according to papers filed in the case. w

In 1973, when the case was filed, 44 percent of the 661 employes in the transportation and claims division were black and 77 percent were in grades 1-4, while only 4 percent held jobs above a GS12.

In 1975, the transportation section was transferred to the General Services Administration while the claims division remained with GAO, but the situation did not improve.

In December 1979, there were 125 employes in the claims division of GAO and 56 percent were black. But 86 percent were still in the lowest grades. There was only one black employe among the 23 above the GS-12 level. A majority of the women employes, who made up 67 percent of the work force, were also concentrated in the lowest-paying jobs, according to court papers.

At the transportation audit branch of GSA, more than half of the 306 employes were either blacks and women and more than 65 percent of them were in low-paying clerical jobs. Only three blacks and seven women were among the 65 highest paid workers.

Scanlon said the Justice Department and the two agencies have agreed to the appointment of a monitor who will insure that promotion goals for blacks are enforced, that training is made available to low-paying employes to qualify for better jobs, that the number of people hired from the outside is limited and that equal employment opportunity records are a factor in the promotion of supervisors.

"I think this will be an incentive to other blacks that feel that they have been intimidated that now they will have the courage to stand up for their rights," said Hortense Tarrar, another of the three plaintiffs.

Tarrar had worked in the transportation branch for 28 years when in 1972, two white women who had worked there about six years were made her supervisors. Tarrar filed a discrimination complaint with the GAO equal opportunity office, and in the following year joined Miller and a second woman, Nestor Calabria, an Asian-American, in the class action suit. Both Tarrar and Calabria have retired. Calabria has moved to Florida.