During his high school years, McCarthy worked in a downtown Houston petroleum statistics office, running a multi-lift printing press.
After several non-parish assignments in San Antonio and Washington, D.C., McCarthy returned to Houston to become pastor of St. Theresa's Parish.
[4] In 1966, McCarthy was appointed executive director of the Bishops' Committee for Spanish-speaking Catholics in San Antonio, where he focused on migrant farm workers.
[5] Its mandate included voter registration, community-run schools, minority-owned and rural cooperatives, and job training programs.
[2] On January 23, 1979, Pope John Paul II appointed McCarthy as an auxiliary bishop of the Diocese of Galveston-Houston.
[6] On December 24, 1985, McCarthy was appointed by John Paul II as bishop of the Diocese of Austin[7] and installed on February 26, 1986.
After returning to Austin, he established the Office of Black Catholics to focus on African American ministry within the diocese.
McCarthy established the Diocesan Law Project, which recruited hundreds of attorneys and interpreters to volunteer legal services for the needy.
His 1993 letter cited the "tragic collapse of standards of decency, morality and honesty in TV, movie and popular music products."
[4] Pope John Paul II accepted McCarthy's letter of resignation as bishop of the Diocese of Austin on Jan 2, 2001.
[10][11] His burial Mass was held at St. William Catholic Church in Round Rock, Texas, and attended by 1,200 people.
A 2019 report by KXAN in Austin revealed that in 1994 McCarthy transferred a priest accused of sexual abuse crimes to another parish.
The report cited documents from a 2003 lawsuit that indicated McCarthy was fully aware of multiple allegations against James O’Connor, a diocese priest.
In a 1994 letter, to O'Connor, McCarthy said that he was appointing him as administrator of St. Thomas Parish in Hamilton, Texas, despite many misgivings:[12] “I am not comfortable placing you in charge of a parish, even a small one, but in order to give you a base for a few months while you rethink your situation, I am happy to go against my better judgment on the basis of Christian charity.
[4] Self described as "slightly tilted toward the left", McCarthy was known for his efforts supporting civil rights, helping workers, increasing minority inclusion in the church and abolishing the death penalty.
"He marched in Selma," said Luci Baines Johnson, "So the Great Society programs my father had in civil rights, these are the causes that were dear to the heart of a young priest.