OBJECTIVE: To study the relative contributions of insurance product (commercial, Medicaid, Medicare), health plan, and physician group to quality of diabetes care. STUDY DESIGN: Cross-sectional observational study using data reported by Minnesota Community Measurement (MNCM) on care provided in 2005. METHODS: Individual performance rates for glycosylated hemoglobin (A1C) level <7%, lowdensity lipoprotein cholesterol (LDL-C) level <100 mg/dL, blood pressure <30/80 mm Hg, documented tobacco-free status, and aspirin use, as well as an all-or-none composite measure (Optimal Diabetes Care), were obtained from MNCM for 57 physician groups. Results included 7169 patients connected with 1 of 8 health plans and 1 of 3 types of insurance product. RESULTS: All factors studied had a relationship to quality results. Of the factors, insurance product has the strongest relationship to A1C, LDL-C, and Optimal Diabetes Care. Health plan had the strongest relationship to tobacco-free status and daily aspirin, and physician group had the strongest relationship to blood pressure control. Physician group results varied more than those for health plan or insurance product on most measures. CONCLUSIONS: All factors studied contribute to diabetes quality results. Reporting both physician group performance and health plan performance may offer a greater opportunity to improve care than reporting only health plan or only physician group results.