In 2015, the Cricket Island Foundation conducted a multimethod assessment of its grantmaking portfolio to examine its impact and inform future decision-making and strategy. The foundation, which supports youth-led social change using a cohort-based model, focuses on emerging and medium-sized organizations and provides capacity-building supports to help organizations achieve greater organizational sustainability. The assessment focused on two of the foundation's three cohorts and found positive trends in five key areas of desired impact: organizational capacity, youth leadership, nonprofit executive leadership, grantee collaboration and learning, and funder policy and practice. The assessment also identified areas for improvement to strengthen future impact, and prompted a review and update of the foundation's ongoing protocols for tracking its progress. This article will explore what was learned from a model of providing long-term capacity-building investments to grassroots organizations, and discuss the ways in which even small foundations can implement meaningful assessment protocols while minimizing data-collection burdens on grantee partners.