Research has shown that low-income students especially struggle with evaluating financial aid offers and completing all necessary requirements to enroll after paying a deposit to a particular college in the spring (Authors, 2009). Motivated by these empirical results, the authors conducted three studies that showed students who were explicitly offered summer assistance from their high school counselors increased the probability of fall college enrollment, suggesting that summer support may be a cost-effective intervention for promoting college enrollment among low-income students. However, several questions remain regarding how summer outreach and counseling could be conducted most efficiently and effectively. The focus of this paper is on investigating the impact of summer support provided by college-aged peer mentors on timely college matriculation among recent high school graduates with articulated college plans. Outreach from peer mentors is a more cost-effective strategy than outreach from professional counselors, and the authors hypothesize that students may be particularly likely to respond to college peers to whom they may feel they can better relate. Through this intervention, peer mentors provided outreach and support to students in four distinct locations: the public school districts in Boston, Lawrence and Springfield (Massachusetts) and a network of charter schools in the Philadelphia metropolitan area. Across the sites, 20 peer mentors provided proactive outreach and the offer of support to 907 students randomly selected from a totally sample of 2,209 students. Peer mentors were each allocated caseloads of students identified as college-intending, based on high school exit surveys and other information-gathering tools utilized by the partnering organizations. The summer counseling interventions to date have provided evidence that outreach and the offer of support in the months after high school graduation positively impact timely college going among college-intending high school graduates. A fuller description of conclusions and recommendations associated with peer mentors as an outreach model relies on postsecondary enrollment data which the authors anticipate receiving by December.