Gerry served as the third abbot of Saint Anselm Abbey until he was appointed an auxiliary bishop of the Diocese of Manchester in New Hampshire in 1986.

[1] In February 1988, Gerry was elected chairman of the Committee on Ecumenical and Interreligious Affairs in the National Conference of Catholic Bishops.

[1] On December 27, 1988, Pope John Paul II named Gerry as the tenth bishop of the Diocese of Portland.

[1] During his 15-year-long tenure, Gerry published a pastoral letter approximately once a year, treating such topics as vocations to the ministry, the sacrament of confirmation, and human sexuality.

He was active in the DIMMID, was appointed member of the Pontifical Council for Interreligious Dialogue and participated in the first Gethsemani Encounter in 1996 together with the Dalai Lama.

[6] On February 4, 2004, Gerry advised the Maine Legislature not to legalize same sex marriage, calling it a violation of "natural law".

[7] On reaching the mandatory retirement age of 75, Gerry submitted his letter of resignation as bishop of Portland to Pope John Paul II in September 2003.