Given the diversity of settings and courses representing academic service-learning practice, a standardized, quantitative instrument to rate the quality level of course design and implementation is needed to optimize educational outcomes for participating students. This article describes a 5-year, multi-institutional process developing the Service-Learning Quality Assessment Tool (SLQAT), a quantitative diagnostic composed of 28 “essential elements” known to promote positive student outcomes in postsecondary service-learning. We discuss the selection and operational definitions for these elements, the assumptions and decisions behind the development of the instrument, the use of expert feedback to develop baseline weights representing the relative importance of each element’s contribution, the creation of rating levels representing element quality, and the development of protocols for the instrument’s scoring and uses. We also reflect upon the challenges of attempting to create a broadly applicable instrument and share plans for additional piloting as well as recommendations for research and practice.