The summer after high school graduation is a largely unexamined stage of college access among underrepresented populations in higher education. Yet two recent studies revealed that anywhere from 10% to 40% of low-income students who have been accepted to college and signaled their intent to enroll reconsider where, and even whether, to matriculate in the months after graduation. This experimental study investigates the effect of providing college counseling to low-income students during the summer. We randomly assigned students at 7 innovative high schools to receive proactive outreach from high school counselors. The treatment focused on addressing financial and information barriers students faced. Results show that providing college counseling to low-income students during the summer months leads to substantial improvements in both the rate and quality of college enrollment. Students in the treatment group were 14 percentage points more likely to enroll immediately in college and 19 percentage points more likely to keep the postsecondary plans they developed during senior year. Policy recommendations include strategies for high schools and/or colleges to provide effective support during the post-high school summer. (Contains 2 tables and 17 footnotes.)