Mons. He was ordained a priest on August 5, 1945 in Šibenik. From 1945 to 1949, he was prefect in the diocesan children"s seminary in Šibenik, as well as a teacher at a state gymnasium. From 1949 to 1951 he was prefect of the archdiocese"s seminary Zmajević in Zadar.
From 1955 to 1958 he served as vice-rector of the seminary.
He was named auxiliary bishop of Zadar on April 30, 1958 and was ordained a bishop of a titular see on July 6 of the same year in the Cathedral of Saint Anastasia. He was made archbishop on August 29, 1969.
He served in this position until February 2, 1996. Marijan Oblak died on February 15, 2008 in Zadar.