[2] He received his episcopal consecration on March 19, 1941, from Archbishop Cantwell, with Bishops Daniel Gercke and Philip George Scher serving as co-consecrators.

[2] In addition to his episcopal duties, McGucken served as pastor at St. Andrew's Parish in Pasadena, California, (1944–1955) and vicar general of the archdiocese (1948–1955).

St. Andrew's parish gave McGucken a farewell celebration at the Pasadena Civic Auditorium, with performances by singer Dennis Day, several choirs, and a US Army color guard.

In his five years as bishop, he authorized, built or approved for development nine parishes, three high schools, 33 new church buildings and one minor seminary.

Architectural critic Allan Temko advocated a bold, new cathedral that would reflect San Francisco's status as a major international urban center.

McGucken added two internationally known architects to his team, Italian-born Pietro Belluschi from the Massachusetts Institute of Technology, who was placed in charge of designs, and Pier Luigi Nervi, an engineer from Rome, who took over structural concerns.

The strikingly modern design which was presented was met with high praise and has been called the "first cathedral truly of our time and in harmony with the liturgical reforms of the Council.

McGucken's stand led one vineyard spokesman to warn that "the Church leaders had better start looking for other financial means to carry out their radical theories.