High-quality child care is related to children's positive developmental outcomes. One way to increase quality of care is to provide training to child care providers. This study used assessment-based training to determine if overall quality of care in center-based preschools could be enhanced. Participants were recruited from six center-based child care programs serving preschool-age children and included program administrators, teachers, teacher aides, and enrolled children. Program administrators (N = 6) were assessed with the Program Administration Scale (Talan & Bloom, 2004), classrooms (N = 14) with the Early Childhood Environment Rating Scale Revised (ECERS-R; Harms, Clifford, & Cryer, 2005) and the Early Language and Literacy Classroom Observation-Research Edition (ELLCO; Smith & Dickinson, 2002), teachers (N = 24) with the Classroom Assessment Scoring System (CLASS; Pianta, La Paro, & Hamre, 2007), and children (N = 135) with an author-created measurement designed to assess typical skills across five child domains. Assessments were administered at two time points and individualized targeted training was provided in between. Results demonstrated that after 7 months of intervention, the largest effect sizes were seen at the program administration and classroom levels and that smaller effect sizes were found at the teacher and child levels. (author abstract)