We examine whether Medicaid recipients receive the same health care services as those on Medicare. We track the services provided to the same individual as they age into Medicare from Medicaid at age 65, becoming dual enrolled. Cost sharing remains negligible across the insurance switch, implying that observed changes in service provision reflect supply-side factors. Service provision increases by about 20 percent upon switching to Medicare, across a range of categories and treatments including high-value care. We find that 60 to 90 percent of the increase in office visits is explained by physicians averse to accepting new Medicaid patients. Geographic variation in our estimates shows that the average increase in utilization is larger in those states with lower Medicaid acceptance rates and higher Medicare acceptance rates. By contrast, we find relatively small increases in care from existing Medicaid providers. This analysis indicates that Medicaid’s smaller provider network plays a large role in limiting service provision.