Precollege outreach programs are an important resource for improving college enrollment for groups that have been historically underrepresented in higher education. But the ability of these programs to serve all eligible students is constrained by resource limitations. This study uses data collected from case studies of four precollege outreach programs to understand how precollege outreach programs may expand the reach of their programs through the use of one seemingly free resource: volunteers. To address this overarching purpose, the study frames volunteering as a type of prosocial behavior and explores the following three questions: How and why do precollege outreach programs use volunteers? What motivations explain a volunteer’s involvement in a precollege outreach program? How do precollege outreach programs encourage individuals to serve as volunteers? The study concludes with recommendations for program administrators and directions for future research.