McCormack was ordained to the priesthood by Cardinal Richard Cushing on February 2, 1960, and then served as an associate pastor at St. James Parish in Salem.

During this time, he also pursued his graduate studies at Boston College, from where he obtained a Master's degree in social work in 1969.

In this position, McCormack was Cardinal Bernard Francis Law's point person on hearing complaints against priests accused of sexual misconduct and removing some of them from active duty.

[1] In 2003, the diocese reached a settlement with the New Hampshire Attorney General's Office, which was investigating the child sex abuse scandal.

[5] Lamontagne claimed that McCormack and other prominent church members wanted a speedy settlement and, in an example of behaving "pastorally" rather than as a litigant, instructed their attorneys to take a moderate stance and eschew hardline legal tactics.

His resignation was accepted on Monday, September 19, 2011, when Pope Benedict XVI appointed then-Auxiliary Bishop Peter Anthony Libasci of the Roman Catholic Diocese of Rockville Centre, New York, as his successor.