Between 1900-1905 Beneshevich worked in libraries in Europe and the Middle East, studying Slavic and Byzantine written sources, and participated in his first archaeological expeditions to the ancient religious center of Mount Athos, Mount Sinai, Egypt, Greece, Asia Minor, and Palestine. He was granted access to handwritten monastic collections in 49 European libraries, and worked in Paris, Vienna, Munich, and Rome, discovering many hitherto-unknown legal monuments in the process. The main focus of his research activities was to reconstruct the history of Greco-Roman law, based on a systematic source base. He also briefly (1903-1904) taught history of canon law at the Alexander Lyceum. His research findings were published in his Master's thesis on The story of the sources of Canonical Law of the Greek Orthodox Church in 1905, for which he received a Master of Church Law. He had also discovered three new fragments of the Codex Sinaiticus (these are now housed at the Russian National Library in Saint Petersburg).