St. Benedict along with Placid and Maurus and other devoted monks left Subiaco after the resentful priest Florentius continuously betrayed them. But St. Benedict being wise and intuitive knew that it simply meant their path was to lead them elsewhere. They arrived to Cassino, a town between Rome and Naples whose people had fallen into misfortune and pagan worship. Here their new calling became clear: to become a spiritual light for Cassino and others to follow. There on the hilltop above the town of Cassino, they built the first oratories and church of Montecassino in 529 AD.

From the start early monastery life at Montecassino was characterized by hard work, including manual labor. For St. Benedict physical labor was an important part of life, inspiring Humility and differentiating themselves from pagan traditions which maintained manual labor as work for slaves. The monks built the first monastery themselves, using the abundant natural resources around them on the hill and in the sacred grove. They incorporated some of the ancient structures such as the cyclopean wall and a guardian tower into their new home. Here another very important element of the Benedictine Order was realized: the importance of community and unity. Previously St. Benedict oversaw 13 monasteries, physically separated. Now they were all together in one location, which allowed St. Benedict to fully understand how to organize monastic life as a single entity rather than as separate systems. The stability and union of this singular position provided the perfect setting for his ultimate miracle: writing The Rule.

As St. Benedict's monastic vision spread they received many visitors, novice monks and in the surrounding areas many women began to dedicate themselves as oblates. Aspiring monks were welcomed and underwent training for a full year before becoming a Benedictine cenobite. As construction finished and the number of inhabitants grew, monks and novice monks began to occupy their time with prayer, study, and other types of work besides physical building. Montecassino became not only a spiritual beacon, but also one of art and culture. Bookmaking, scriptoria, art preservation and production, as well as preservation of classical literature were among some of the major jobs the residents of the abbey occupied themselves with during their daily life. The scriptorium and school of copyists at Montecassino would increase in size dramatically through the centuries, especially under the abbacy of Desiderius.

The early period of Montecassino was a time of stability and growth. St. Benedict's influence was spreading far and wide, his charisma touching even the wickedest of visitors. The foundation of Montecassino was the creation of a sacred family, whose generations have maintained their founding father's vision of a holy, pure, and charitable life for more than 15 centuries.