This article seeks to examine 2 federally funded early literacy projects, one an Early Reading First demonstration project, the other an Early Childhood Educators Professional Development Research Study. It describes the respective professional development models that include on-site mentoring support to improve teacher quality. The article illustrates the use of child-level and classroom data to inform an individualized mentoring protocol to impact change in both teacher knowledge and classroom practice, with the ultimate goal of improving outcomes for children in early childhood classrooms. (Contains 1 table.)