Background: OCM was a voluntary episode-based alternative payment model designed to improve the value of care for fee-for-service Medicare beneficiaries receiving systemic therapy for cancer. Participating practices received monthly enhanced oncology services (MEOS) care coordination payments and could receive additional payments (or penalties) if they met quality and total episode spending goals during 6-month episodes. Methods: We used a difference-in-differences approach to evaluate OCM impacts on Medicare payments, utilization, and quality measures during 6-month episodes before (July ‘14-January ’16) and after (July ‘16-June ‘21) OCM’s start. Patient-episodes were attributed to OCM-participating practices (n = 202) or propensity-matched comparison practices (n = 534). Statistical significance was defined as p≤0.10 to avoid missing program impacts. Results: Total episode payments (TEP) for 6-month OCM episodes increased from 29,120 in the baseline period to 35,467 in the OCM period (+21.8%). In reference to comparison episodes, OCM led to a 499 relative reduction in TEP (90%CI -771, -227, -1.7% relative to baseline.) OCM had no significant impact on TEP for low-risk breast, prostate, and bladder cancers, and OCM led to a relative decrease of 755 (CI -1140, -371) for all other higher risk cancers. Reductions in TEP were largest for high-risk breast cancer, lymphoma, lung cancer and colorectal cancer. The overall OCM impact on TEP was attributable to relative reductions in both Part A payments (-152, [CI -257, -47]) and Part B payments (-276, [CI -459, -92]). There was no OCM impact on Part D payments. While OCM had no impact on Part B chemotherapy payments, OCM reduced Part B non-chemotherapy drug payments by 251 (CI -330, -173; -9.3%). Utilization analyses showed no impact of OCM on ED visits or hospitalizations, but OCM reduced the likelihood of ICU admission by 0.6 percentage points (PP; CI -1.0, -0.1, -5.4%). OCM had no impact on initial chemotherapy regimen selection, but OCM led to greater use of biosimilar cancer therapies and value sensitive changes in the use of antiemetics, bone supportive medications, and WBC growth factors (including greater use of biosimilar WBC growth factors; all p < 0.10). OCM reduced hospitalizations in the last 30 days of life by 0.8 PP (CI -1.6, -0.1; -1.5%) with no impact on use of chemotherapy or hospice at the end of life. Despite OCM-related TEP reductions, OCM resulted in net losses to Medicare after accounting for MEOS and performance-based payments. Conclusions: OCM led to reductions in TEP with similar or improved quality. Reductions in TEP were greatest for common, high-cost cancer types and were driven primarily by changes in use of supportive care medications. The Medicare Enhancing Oncology Model will build on the experience of OCM to further the goal of improving the quality and value of cancer care for Medicare beneficiaries.