Gebhard dedicated the monastery church to Pope Gregory the Great and settled the abbey with monks descending from Einsiedeln.

As Petershausen sided with the papacy in the Investiture Controversy, Gebhard III in 1103 was deposed at the instigation of Emperor Henry IV.

Embroiled in constant disputes over land and jurisdiction with the nearby city and bishopric of Constance as well as with Swabian nobles like the Counts of Montfort, the abbots turned to the Imperial Hohenstaufen dynasty for support.

[1] During the Council of Constance (1414–18), the German king Sigismund of Luxembourg stayed at the Petershausen and the abbot was even given the pontifical vestments from Antipope John XXIII.

The abbey is freed after Constance, which had officially become Protestant in 1530, is conquered by the Spanish troops of Charles V during the Schmalkaldic War, forcibly re-Catholicized, stripped of its status as a free imperial city and absorbed into Further Austria.