A Resident Supervision Index (RSI) developed by our research team quantifies the intensity of resident supervision in graduate medical education, with the goal of testing for progressive independence. The 4-part RSI method includes a survey instrument for staff and residents (RSI Inventory), a strategy to score survey responses, a theoretical framework (patient centered optimal supervision), and a statistical model that accounts for the presence or absence of supervision and the intensity of patient care. The RSI Inventory data came from 140 outpatient encounters involving 57 residents and 37 attending physicians during a 3-month period at a Department of Veterans Affairs outpatient clinic. Responses are scored to quantitatively measure the intensity of resident supervision across 10 levels of patient services (staff is absent, is present, participated, or provided care with or without a resident), case discussion (resident-staff interaction), and oversight (staff reviewed case, reviewed medical chart, consulted with staff, or assessed patient). Scores are analyzed by level and for patient care using a 2-part model (supervision initiated [yes or no] versus intensity once supervision was initiated). All resident encounters had patient care supervision, resident oversight, or both. Consistent with the progressive independence hypothesis, residents were 1.72 (P = .019) times more likely to be fully responsible for patient care with each additional postgraduate year. Decreasing case complexity, increasing clinic workload, and advanced nonmedical degrees among attending staff were negatively associated with supervision intensity, although associations varied by supervision level. These data are consistent with the progressive independence hypothesis in graduate medical education and offer empirical support for the 4-part RSI method to quantify the intensity of resident supervision for research, program evaluation, and resident assessment purposes. Before informing policy, however, more scientific research in actual teaching settings is needed to better understand the relationships among patient outcomes, clinic workload, case complexity, and graduate medical education experience in resident supervision and professional development.