The Rev. William A. Beal, 56, the rector of St. John's Episcopal Church in Chevy Chase for the past 20 years, died at his home in Chevy Chase Sunday following a heart attack.

Mr. Beal was born in Washington and spent his life in this area. He graduated from old Central High School in Washington, served as a navy aviator in World War II, and graduated from the University of Maryland in 1949.

He earned a master of divinity degree from Virginia Theological Seminary in Alexandria. He was Episcopal chaplain at the University of Maryland from 1952 to 1956 and then went to St. John's as associate rector. He was named rector in 1959 and continued in that position until his death.

In addition to his duties in the parish, Mr. Beal held several posts in the Episcopal Diocese of Washington and in service organizations. He was secretary of the standing committee of the Washington Diocese and a member of the ecclesiastical court. He also had served as chairman of the diocesan departments of Christian education, college work, and church extension and church management, and of the hospice for the terminally ill committee. He was a founding member of the Overseas Mission Society and Companions in World Mission.

Mr. Beal also was a member of the clinical research subpanel of the National Institute of Allergies and Infectious Diseases. He was chaplain of the Bethesda Fire Board and a member of the Montgomery County Senior Nutrition Program, as well as being active in several other endeavors.

Survivors include his wife, Patricia, of the home, and three children, Nancy, of New York City, and Ashby and Philip, both of the home.