Despite improvements in care for patients with cancer, and in their survival rates, it is not clear that best practices are uniformly delivered to patients. We measured the quality of outpatient cancer care, using validated quality measures, in a consortium of thirty-six outpatient oncology practices in Michigan. We discovered that throughout the measurement period, for breast and colorectal cancer care, there was a more than 85 percent rate of adherence to quality care processes. For end-of-life care processes, the adherence rate was 73 percent, and for symptom and toxicity management care processes, adherence was 56 percent. In particular, we found variations in care around the fundamental oncologic task of management of cancer pain. To address quality gaps, we developed interventions to improve adherence to treatment guidelines, improve pain management, and incorporate palliative care into oncology practice. We concluded that statewide consortia that assume much of the cost burden of quality improvement activities can bring together oncology providers and payers to measure quality and design interventions to improve care.