Nurses who have struck three Prince George's County-owned hospitals for a month voted last night to approve a contract agreed to by negotiators Wednesday and to return to work, starting Saturday.

As the nurses' union meeting at the Riverdale Elks Lodge broke up with tears, smiles and the singing of "Solidarity Forever," union President Carolyn Larkin expressed delight at the outcome in which she said the nurses voted "overwhelmingly" for the contract. The vote count was not announced. About 300 nurses attended the meeting.

Picketing at the three facilities--Prince George's General Hospital, Greater Laurel-Beltsville Hospital and the Bowie Health Center--was called off yesterday following the tentative accord reached by negotiators for the Maryland Nurses Association and Community Hospitals and Health Care Systems Inc.

The issue that had delayed settlement--whether 20 of the strikers will get their specialty nursing positions back--will be submitted to binding arbitration under the contract agreed to last night.

Union officials have said that about 500 of 650 nurses at the three facilities participated in the strike, which began Aug. 29.

Spokesmen for the medical facilities, which hired temporary nurses, said they continued to provide adequate care.

A tentative accord on all but the disputed positions was reached during a marathon bargaining session that ended early Saturday.

The question to be decided by binding arbitration within four weeks is whether 20 of the strikers will be allowed to resume their specialty nursing positions, which were given to others during the strike. A hospital corporation spokesman said the nurses previously employed in those posts, primarily in emergency and intensive care units, would be reassigned to other nursing jobs or given administrative leave with pay pending the outcome of the arbitration.

The contract calls for a 35-cent-an-hour raise retroactive to Aug. 1, to be followed by another 35-cent-an-hour raise in February, and adjustments in weekend and night differentials.

The nurses, hitherto paid between $17,000 and $25,000 annually, will receive $18,000 to $27,600.