In 1766 he entered the Benedictine Monastery in Melk Abbey where he served as Benedictine monk, and then Prior from 1784 to 1786. In 1786, he was Abbot of the Monastery of Lilienfeld, and from 1789 in Kremsmünster Monastery.
Stadler was among the most prominent personalities of Viennese musical life at the turn of the 18th and 19th centuries. He befriended Mozart, Joseph Haydn, Ludwig van Beethoven and Franz Schubert and wrote numerous essays on Mozart. He also completed some of Mozart's unfinished works. He worked on an unfinished Materialen zur Geschichte der Musik unter den österreichischen Regenten (Materials on the History of Music under the Austrian Regency), regarded as the first history of music in Austria. Most of his works are in the Austrian National Library and the Gesellschaft der Musikfreunde in Vienna.
- Oratorium Die Befreyung von Jerusalem (The Deliverance of Jerusalem), 1813
- Church music, including two Requiems and numerous smaller church music
- Works for keyboard instruments
- Music theory and historical writings
- Classical Composers Database – Classical music composers of all periods and countries, with biographies and work lists
- MusicWeb International – CD reviews, composer articles, timelines, concert and book reviews
- European magazine's selection of best classical music recordings from different time periods