The 10th century was a period of rebuilding for Montecassino after a second destruction and the 11th century then was a time considered a "golden age" for the abbey. The abbot Desiderius, serving from 1058 until 1087, was responsible for this greatly prosperous era. Montecassino enjoyed a period of political stability and renown due to Desiderius' influential decision to reverse previous anti-Norman policies, seeking a road of peace and cooperation. This was also during the time of the great schism between the Eastern and Western church, but despite this, he maintained a good relationship with Constantinople, even asking them to participate in the rebuilding project of the church of Montecassino. The new church was built on a grander than ever scale, with the help of many artists and architects from Byzantium. Some elements of this 11th century church can still be seen today at Montecassino. The consecration of the finished church in 1071 was a highly attended occasion. The crowd included bishops, Norman royalty, archbishops, and monks, and is widely considered to have been one of the most spectacular events of the 11th century.

Under the era of Desiderius, Montecassino became an even larger cultural center. The number of cenobites grew to upwards of 200 and as a result they were able to increase the size of their manuscript library drastically. Copying and preserving history, a longtime practice of the hardworking monks of Montecassino, grew in production. They became recognized for the scriptorium and its great number of scribes, as well as the extremely talented painters of miniatures. The amount of precious copies made of documents, books, and letters was overwhelming, both in size and importance.

After his abbacy Desiderius went on to become Pope Victor III. Regarding Montecassino, and demonstrating its power and influence of this era, Pope Urbano II said on March 27th, 1097: "This place truly was and remains a relief for our poor, a refuge for those fleeing, an endless peace for the poor children of the Apostolic See."