Background: Biosimilar adoption offers the potential to save significant cost while maintaining high quality of care. The Oncology Care Model (OCM) is structured to reward practices for decreasing total cost of care (TCOC) compared to historical baseline prices that are adjusted by a trend factor accounting for the rising cost of oncology care. Practices are rewarded for bending the cost curve by utilizing lower cost medications. Biosimilar options were introduced for 3 mainstay therapeutic classes in oncology, bevacizumab and trastuzumab in 2019, and rituximab in 2020. This led to a concerted approach for biosimilar adoption in The US Oncology Network (The Network) as an opportunity to reduce TCOC. Here we describe utilization and the financial impact of biosimilar adoption in The Network during OCM performance period 8 (PP8) which enrolled patients from 1/2/2020 to 7/1/2020. Methods: Claims data for the 14 US Oncology Network practices participating in the OCM were used to determine biosimilar utilization for bevacizumab, trastuzumab, and rituximab therapeutic classes. The impact of biosimilar utilization on TCOC was measured by comparing the cost of each dose of a biosimilar vs the estimated cost if the more expensive innovator agent had been used instead. Results: Biosimilar utilization increased for each therapeutic class from prior performance periods. Biosimilar use for bevacizumab was 0% in PP6, 5% in PP7 and 43% in PP8. For trastuzumab, utilization was 0% in PP6, 4% in PP7 and 33% in PP8. Rituximab biosimilar utilization was 0% in PP6, 2% in PP7 and 41% in PP8. We compared the actual cost of these three medications in our OCM claims in PP8 vs. the calculated cost based on Medicare reimbursement as ASP + 6% minus sequestration if the more expensive innovator drugs had been used entirely. The difference in the actual cost vs estimated cost led to a savings of $6.61 million by using the biosimilars over innovator drugs. Conclusions: The increased utilization of biosimilars in The Network generated significant savings in OCM. Continued adoption of biosimilars will increase savings to Medicare in the Oncology Care Model. We estimate that 100% Network adoption of these three biosimilars could save nearly 1.5% of the TCOC in our Network compared to continued use of innovator drugs.