White mold (Sclerotinia sclerotiorum (Lib.) de Bary) often results in substantial yield and quality losses in winter oilseed rape (Brassica napus L.; OSR). This study investigated the tolerance levels of four commonly cultivated OSR hybrids (Architect, Bluestar, PT271, and Umberto) to white mold infection and assessed the effects of fungal infection on yield. Artificial inoculation with mycelial disks of S. sclerotiorum was performed on the four OSR hybrids during the siliqua formation stage (BBCH 71-79) over three consecutive growing seasons (2020/21 to 2022/23). The levels of OSR plant infection and yield parameters (thousand-seed weight (TSW), moisture, protein, and oil content) were determined. The hybrids exhibited varying levels of tolerance to the pathogen, and these differences were affected by the growing season. The Architect hybrid proved to be the most susceptible in the 2020/21 season, while no differences were observed in the following growing seasons. Infection resulted in yield reductions of up to 93% and impacted protein and oil content, and TSW to varying extents, while moisture content remained unaffected. These results underscore the importance of selecting S. sclerotiorum-resistant oilseed rape hybrids to maintain yield quality and to inform integrated pest management (IPM) strategies tailored to the conditions of each growing season.