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.