After studying the humanities and philosophy at Freising and Ingolstadt, he entered the Benedictine monastery of St. Emmeram at Ratisbon, where he took vows on 8 December 1728, and adopted the name "Frobenius".
Though leaning towards the Leibniz-Wolffian philosophy, he rejected many of its teachings, such as the cosmological optimism of Leibniz and the mechanism of Wolff, and was rather an eclectic than a slavish follower of any one system.
During his reign the course given in the natural sciences at St. Emmeram became famous throughout Germany and drew scholars not only from the Benedictine monasteries of Bavaria, but also from the houses of other religious orders.
In order to promote the study of Holy Scripture, Forster called the learned Maurist philologist, Charles Lancelot of St-Germain-des-Prés, who instructed the monks of St. Emmeram in Semitic languages from 1 October 1771, to 27 May 1775.
From a codex preserved in the library of the cathedral chapter at Freising he edited the decrees of the Synod of Aschheim and made a German translation of it for "Abhandlungen der Bayr.