He served as the first abbot of the Abbey of St. Gall, a Benedictine monastery near where the city of St. Gallen, now in Switzerland, developed.

[3] Othmar united into a monastery the monks that lived about the cell of St. Gall, according to the Rule of St. Columban, and became their first abbot.

In 747, as a part of the reform movement of Church institutions in Alamannia, he introduced the Benedictine Rule,[2] which was to remain in effect until the secularization and closure of the monastery in 1805.

Othmar also provided for the needs of the surrounding community, building an almshouse as well as the first leprosarium in what is now Switzerland, as well as others in France and Germany.

[2] In 759, Counts Warin and Ruodhart tried to gain possession of some property belonging to St. Gall, Othmar fearlessly resisted their demands.

Hereupon they captured him while he was on a journey to Constance, and held him prisoner, first at the castle of Bodmann, then on the island of Werd in the Rhine.

[5] Othmar's cult began to spread soon after his death, and next to Maurice and Gall, he is one of the most popular saint in Switzerland.