A team from the University of Pennsylvania was funded by the William Penn Foundation to conduct an inquiry of Keystone STARS. The goal of this inquiry was to provide a broad look at Keystone STARS to inform future revisions and evaluation of the system as part of Pennsylvania’s Race to the Top Early Learning Challenge grant (2013-2018). The inquiry focused on providing an overarching look at Keystone STARS with respect to three major areas and presents a detailed review of the data and findings for each of the three aspects: Child outcomes: examining the relations between Keystone STARS and children’s overall developmental competencies. Quality components: investigating the extent of evidence from theory, empirical research, and practitioner expertise linking each of the Keystone STARS quality components to child outcomes. Systems approach to rating quality and guiding improvements: examining overall features of the system that could be improved to enhance the effectiveness and efficiency of the system. The authors conclude with an overview of the lessons learned and point to promising areas of reform for improving Keystone STARS for the children of Pennsylvania.