Coadjutor bishop
Gibson was consecrated as Suffragan bishop of the Diocese of Virginia in 1949 and in 1954 the diocesan convention elected him as Coadjutor bishop of Virginia. In 1961 he became the diocesan bishop. In addition to his diocesan duties, including support for the ordination of women as priests, Bishop Gibson was an outspoken supporter of ecumenism, and served as chairman of the Consultation on Church Union in the 1960s, although their plan to merge eight major Protestant denominations into a 24-million-member church was never consummated. He also served as vice president of the House of Bishops.