Roberta Catherine McBride, 65, headmistress of St. Agnes (Episcopal) School in Alexandria until two years ago, died Wednesday at Goodwin House in Alexandria following a series of strokes.

Miss McBride went to St. Agnes in 1951 as headmistress, the third person to hold that position. While there, she initiated a student's volunteer program to assist families recommended by the local welfare agency.

Before joining St. Agnes, she had been on the faculties of the Shore Country Day Schol and the Northhampton School for Girls in New England.

Miss McBride was born in Leavenworth, Kan. In 1934, she earned a bachelor's degree from Smith College and, in 1936, a master's degree from Columbia University. She also studied at the Sorbonne in Paris.

She was active in volunteer work for many years, as a Red Cross Grey Lady working with mentally disturbed war veterans and at the tuberculosis clinic at St. Luke's Hospital in New York City. She was director for 10 years of the New York Herald Tribune's Summer Fresh Air Camp, and for five years was director of the YWCA Camp in Hartford, Conn.

Miss McBride lived at St. Agnes School until moving to Goodwin House in 1976 because of ill health.

She received an honorary doctorate in humane letters from the Virginia Theological Seminary in 1975.

There are no immediate survivors.

It is suggested that expressions of sympathy may be in the form of contributions to Emmanuel Episcopal Church in Alexandria or the Roberta C. McBride scholarship fund of St. Agnes School.