Public reporting on the quality of ambulatory health care is growing, but knowledge of how physician groups respond to such reporting has not kept pace. We examined responses to public reporting on the quality of diabetes care in 409 primary care clinics within seventeen large, multispecialty physician groups. We determined that a focus on publicly reported metrics, along with participation in large or externally sponsored projects, increased a clinic's implementation of diabetes improvement interventions. Clinics were also more likely to implement interventions in more recent years. Public reporting helped drive both early implementation of a single intervention and ongoing implementation of multiple simultaneous interventions. To fully engage physician groups, accountability metrics should be structured to capture incremental improvements in quality, thereby rewarding both early and ongoing improvement activities.