During the Early Middle Ages it was the home of a parish church that covered a large parish. This Church of St. Eusebius was probably built in the 6th or 7th century by the Bishop of Lausanne. The church is mentioned several times between 852 and 875. In the 9th century, the parish was split into several independent parishes. As the parish shrunk in size, the church gradually lost its former importance, but it remained the center of the Decanate of Ogo until the 16th century. The deanery covered the whole Saanen valley to Treyvaux, the Jaun and Sionge valleys and extended west to Glâne. Bulle probably came under the secular power of the Bishop of Lausanne as early as the 6th century, and together with Avenches and Curtilles formed the territory originally owned by the bishop.