Almost 70 percent of the families on the waiting list for public housing in Montgomery County are members of minority groups, but when the county's newest public housing complex opened in Olney last week, the residents were a carefully integrated 50 percent whites and 50 percent minorities.

The racial balance was the result of an "integration maintenance" system the county Housing Opportunity Commission has used since the beginning of the year to assure that the county's larger public housing projects are racially balanced.

Under the policy, half the apartments in the Olney project were allocated to the 30 percent of the applicants who are white and half were available to the 70 percent who are not. Some white applicants got in ahead of nonwhite families who were ahead of them on the list, county officials concede.

The racial quota system for selecting new tenants in about 320 of the county's 950 public housing units was submitted to the U.S. Department of Housing and Urban Development for approval nearly a year ago, but the agency has so far not responded, said Bernard L. Tetreault, director of the Housing Opportunities Commission.

The Reagan administration generally has opposed racial quotas, but has delayed decisions on the use of systems like Montgomery County's by public housing projects in Charlottesville, Va., and New York City.

The commission voted last December to initiate the system because the members saw that "if we did nothing, the cluster developments [apartment complexes] would tend toward, and probably eventually become, heavily minority," Tetreault said.

The racial balance policy is used only in the county-owned apartment buildings, which provide about one-third of the public housing. The remaining units are town houses and single-family detached homes scattered in Montgomery communities and are filled on a first-come-first-served basis.

Montgomery County's goal is to achieve a balance of half white and half minority residents in an apartment building, but no action is taken until the share of minority residents exceeds 70 percent, Tetreault said.

Since the populations of nearly all the county's larger projects are already over 70 percent minority, vacancies are being filled under the quota system.

The system was used in selecting tenants for the new 49-unit Town Center Place facility in Olney, which opened last week. The project's racial composition is 50 percent white and 50 percent minorities, according to Joyce Siegel, an HOC spokeswoman.

Peg McRory, a longtime housing activitist in Montgomery County and former housing consultant to the County Council, called the quota system "unfortunate but necessary. It is so difficult to get public housing built in Montgomery County, and if it became all minority, it would be a hopeless situation. . . . We're racist in Montgomery County and if we see something all black, we run and scream and jump up and down."

Montgomery County NAACP President Roscoe Nix said the organization has not taken an official position on the HOC admissions policy but believes "this is something that deserves serious consideration. We don't want segregated housing but the question is, who needs the housing. Is it right to have a policy where you discriminate?"

Nix said he will instruct the county NAACP's housing committee to study the policy.

"This issue is very important to HUD and we are seeking a workable solution," said Margaret White, manager of the HUD D.C.-area field office. "We want to be certain that when we do issue a position it is one consistent with statutes and appropriate federal regulations."

White said that it "would not be a viable solution" to the problem for HUD to cut off housing subsidies to Montgomery County if HUD ultimately disapproves the county's admissions policy for subsidized housing.

White could not say, however, what action HUD would take if it did rule against the local housing authority.

In addition to the Montgomery plan, the department has pending before it a similar integration maintenance policy that the Charlottesville public housing agency has been using since 1980. HUD was asked for a ruling on the Charlottesville plan more than a year ago, after black leaders protested that the tenant selection process discriminated against blacks.

The Charlottesville public housing agency, which limits black residents to a maximum of 65 percent and a minimum of 35 percent of its housing spaces, still receives HUD funds, according to Ronald R. Tweel, the housing authority's attorney. "It's business as usual," he said. "We haven't heard from HUD in about eight months" regarding the tenant selection policy.

HUD refused to rule on a tenant selection policy in Starrett City, a giant, New York State-operated public housing project in Brooklyn that limited minorities to 35 percent of the residents.

Civil rights groups sued Starrett City and the state of New York, charging that the quota system violated federal antidiscrimination laws. The suit was settled in May 1984 when the state agreed to make 40 percent of the units available to minority tenants. The Justice Department then filed a civil suit charging the Starrett City quota system discriminated against minorities. The case is still in court, according to an attorney.

Antonio Monroig, HUD assistant secretary for fair housing and equal opportunity, said a quota system "makes no sense." Monroig, who has been talking recently with fair housing groups at meetings in Chicago, Washington and San Francisco, said HUD "wants to guarantee freedom of access" to public housing for all races, but does not want quotas used.

It is too soon to tell what effect the admissions policy is having because a tight housing market keeps the annual turnover rate of apartments at about 10 percent, Tetreault said.

As of the 1980 census, Montgomery County's population was about 85 percent white, 8.8 percent black and 6 percent Asian and other.

About 4,200 families and elderly citizens are on the HOC's waiting list for public housing, about three-fourths of them families, according to Tetreault. The waiting time varies according to family size but averages from 2 1/2 to 3 years, he added.

The admissions policy is a result of the housing commission's recognition that "we needed to intervene but we wanted to minimize the impact," Tetreault said.

Asked the reasons for the heavily black population in public housing, he cited "a stereotyping of public housing residents." In addition, "we get turndowns from [white] families in cluster units, so the percentage of acceptances in cluster units by minority is higher."