Born at Gunzenhausen, Ansbach, in the region of Franconia, Osiander studied at the University of Ingolstadt before being ordained as a Catholic priest in 1520 in Nuremberg.

During the First Diet of Nuremberg (1522), he met Albert of Prussia, Grand Master of the Teutonic Knights, and played an important role in converting him to Lutheranism.

He also played a prominent role in the debate which led to the city of Nuremberg's adoption of the Reformation in 1525, and in the same year Osiander married.

In 1533, Brandenburg-Nuernbergische Kirchenordnung vom Jahre 1533 was published, with Osiander assisting in both the source material and the final editing.

[2] In 1543, Osiander oversaw the publication of the book De revolutionibus orbium coelestium (On the revolutions of the celestial spheres) by Copernicus.

He added a preface suggesting that the model described in the book was not necessarily true, or even probable, but was useful for computational purposes.

Flacius' opposing view was that God justifies us by Christ's work of obedience on the cross, not by his presence in us.