A tentative agreement was reached last night averting a threatened strike by employes of 40 cafeterias at federal government buildings where more than 90,000 government workers eat.

The agreement reached between the union that represents the 1,000 cafeteria employes and the private corporation that operates the cafeterias is subject to ratification today by the union members.

About 450 members of the Hotel and Restaurant Employees Union, Local 25, voted unanimously Saturday to strike if a settlement was not reached by 12:01 a.m. today, when the old contract with Guest Services Inc. expired.

The tentative settlement was reached late last night after hours of bargaining at the Hay-Adams hotel, according to federal mediator Gilbert McCutcheon.

Details of the settlement could not be learned immediately. The parties reportedly agreed not to divulge details before today's vote, which is to be held at 5 p.m. at the Shiloh Baptist Church in Northwest.

However, Ron Richardson, executive secretary and treasurer of the union, said it was "the best contract we've ever had" from the corporation. Richardson said earlier that wages and medical insurance were the key issues. He said that cafeteria workers were earning an average of about $4.50 under the old contract. He also said that under terms offered by Guest Services before the settlement was reached, they could not afford family medical insurance. While workers received free individual coverage under the old agreement, they were required to pay about $110 for family hospitalization coverage, he said.

Richardson said about 90 percent of the cafeteria workers are women, including many single parents who need family hospitalization coverage. Only about 3 percent have such coverage, he said. One company offer, made before the agreement was reached, would have paid $30 monthly toward hospitalization, Richardson said.

Contacted before the settlement, Guest Services' Vice President Bill McGrath would not discuss negotiations, but said Guest already provides free dental, legal and optical services, which the company considers a "generous" package of benefits. Richardson said those benefits are standard to Local 25's 10,000 members throughout Washington. He said the hospitalization coverage is crucial to cafeteria workers because their pay is low compared to most unionized workers in the area.

The Federal Mediation and Conciliation Service had entered the contract talks after the Saturday strike vote.

Despite McGrath's earlier pledge that "we are not going to inconvenience our guests," Richardson had said he doubted Guest could have operated without the union because most of its food is fresh-cooked. "It's not the frozen stuff you get at most cafeterias. It's good," he said.

A strike would have affected operations at dozens of federal agencies, including U.S. District Court, Post Office, the Federal Bureau of Investigation, Central Intelligence Agency, State and Justice Departments, National Institutes of Health, and others.