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: 1. Child outcomes. This inquiry examined the relations between Keystone STARS and children's overall developmental competencies. 2. Quality components. This inquiry investigated the extent of evidence from theory, empirical research, and practitioner expertise linking each of the Keystone STARS quality components to child outcomes. 3. Systems approach to rating quality and guiding improvements. This inquiry examined overall features of the system that could be improved to enhance the effectiveness and efficiency of the system. (author abstract)