 Stadler was ordained a priest in Rome on June 6, 1868, after which he returned to Zagreb where he worked as a professor at a seminary and later a university professor at the Catholic Faculty of Theology of the University of Zagreb.In 1881, the Catholic Church hierarchy in Bosnia and Herzegovina was reinstated after nearly seven centuries, when the last bishop of Bosnia was evicted by Bosnian ban Kulin and left Bosnia for Đakovo.Pope Leo XIII named Stadler as the first archbishop of Vrhbosna in Sarajevo.