In many applied youth development settings, including out-of-school time (OST) programs, volunteers play essential roles (Brennan, 2005). In some, volunteers are integral to service delivery -- for example, serving as mentors. In others, volunteers help link youth-serving organizations or their participants with needed resources, assets, or opportunities (Brennan, 2007). In order to support youth-serving organizations' efforts to engage volunteers sustainably, the authors developed and tested the Mixed-Method, Open-Ended Volunteer Experiences (MOVE) Assessment, a two-phase approach to identifying and monitoring the benefits volunteers associate with their service in OST programs. Building on traditional sequential exploratory mixed-method designs (Creswell et al., 2003), MOVE begins by qualitatively exploring and documenting volunteer experiences. Findings then guide design and implementation of a recurring quantitative assessment that can become the foundation for continuous improvement in volunteer management. This paper introduces MOVE by describing its application in ANYTOWN, an OST program sponsored by Community Tampa Bay that focuses on promoting inclusiveness, community involvement, and social responsibility among high school students.