Attending high-quality early childhood care and education (ECCE) is associated with higher cognitive and social-emotional skills, especially for children growing up in poverty, but access to high-quality ECCE is limited. This study capitalizes on the random assignment design of the Head Start Impact Study to better understand whether the randomized offer to attend Head Start, a free comprehensive child development program for low-income and at-risk children, raises the quality of ECCE in which children enroll. Multinomial logistic regression was used to isolate the intent-to-treat impacts of random assignment to Head Start on ECCE quality from impacts on enrollment in formal ECCE. Results indicate that children randomly assigned to receive Head Start (treatment), compared to children in the control group, were more likely to enroll in high-quality and, to a lesser extent, low-quality ECCE. Treatment impacts were largest at the high end of the quality distribution, were driven by increased enrollment in Head Start, and differed for 3- and 4-year-olds. These results highlight the important role of Head Start in providing high-quality ECCE for low-income children. (author abstract)