Effects of a 1-semester professional development (PD) intervention that included expert coaching with Head Start teachers were investigated in a randomized controlled trial with 88 teachers and 759 children. Differential effects of technologically mediated (remote) versus in-person (on-site) delivery of individualized coaching with teachers also were examined in a random assignment design. Hierarchical linear model analyses revealed positive PD intervention effects on general classroom environment (d = 0.99) and classroom supports for early literacy and language development (d = 0.92), and on children's letter knowledge (d = 0.29), blending skills (d = 0.18), writing (d = 0.17), and concepts about print (d = 0.22). No significant intervention effects on teaching practices and children's outcomes related to oral language were found. There were no differential effects of remote versus on-site delivery of literacy coaching. (Contains 5 tables.)