Workers at Washington Gas Light Co. voted yesterday to accept new contract offers from the utility and to go back to work today, ending a strike that began June 5.

About 1,750 workers belong to the two unions that voted by large margins to end the first strike in 25 years against the area's supplier of natural gas.

During the strike by gas service workers and office workers, the company assigned managers to handle emergencies and disruptions in service while postponing routine calls and new installations.

Washington Gas has about 590,000 customers, including 400,000 residential users of natural gas.

"We're pleased it's over," company spokeswoman Cate Barnett said last night of the strike by members of the International Union of Gas Workers and Local 2 of the Office and Professional Employees International Union.

"We feel very satisfied with the company's offer," said Patrick Estrada-Palma, recording secretary of the gas workers union, an independent organization with about 1,275 members at Washington Gas.

Company spokeswoman Barnett said the contracts offered both unions included wage increases of 4.25 percent in each of the first two years and 4.7 percent in the third.

In addition, she said, the company agreed that pay bargaining could be reopened in the third year if the inflation rate for the year starting in March 1987 exceeds 5.5 percent.

The third-year reopener provision includes the right to strike.

The company's last offer before the strike included wage increases of 4.25 percent each year for three years.

Barnett said pay rates for members of the unions would range from $10.88 an hour to $19.24 an hour in the third year of the agreement.

Estrada-Palma said his union voted by a 4-to-1 margin to accept the offer. Officials of the other union, which has about 500 members, could not be reached, but their margin of approval was described by the company as higher.

Estrada-Palma said members of the gas workers union were pleased by the assurances of job security given during bargaining by the utility's chairman, Donald J. Heim.

While no guarantees could be provided, said Washington Gas spokeswoman Barnett, "The company told the union it had no plans for layoffs in the near future."

Estrada-Palma said the agreement included improvement in pensions and in the company's sick-leave policy.

Barnett said management personnel "did extremely well in keeping up essential services" during the strike.