Gaining Early Awareness and Readiness for Undergraduate Programs (GEAR UP) is a federal program designed to promote postsecondary readiness and success among low-income students. Some evidence suggests that this program promotes college enrollment and persistence, but GEAR UP may include a wide variety of services, and it is unclear which ones actually contribute to these apparent overall effects. The present study investigates this issue using doubly robust propensity score analyses to provide stronger causal conclusions. Four general service types and seven specific services were examined; the results provide important implications for GEAR UP and other programs designed to promote postsecondary attainment.