Medicare is the largest single program providing explicit support for graduate medical education (GME) in the United States, funding about 20% of all direct medical education (DGME) costs. However, Medicare also enforces a time-invariant, hospital-specific cap on the number of residents it supports per year. Despite the enormous public investment in graduate medical education, previous research has not addressed how Medicare’s DGME funding caps affect the number of residents per hospital, the general healthcare workforce, or healthcare quality. Exploiting a policy stipulation from the Affordable Care and Patient Protection Act, this paper examines the effect of Medicare-funded DGME on 1) the supply of medical residents, physicians, and physician assistants at the county level and 2) the quality of healthcare provision at the hospital level. The results suggest that an increased DGME funding cap is correlated with an increase in the county-level number of residents, but with a two-year lag from the date of the cap increase. The number of primary care residents is significantly higher beginning three years after the initial cap increase, and the number of nurse practitioners shows a significant increase four years after the cap is raised. Within the first five years after a cap increase, no significant change was detected in the county-level supply of physicians. No significant change in quality was detected at the hospital level.