This multiple-baseline, single case design study investigated the effects of a multi-component professional development program to increase educators' use of explicit vocabulary instruction during small group interactive shared book reading sessions in Early Head Start classrooms. The effects of the program were examined across four educators and 2-3 of their students (n = 9 students). Educators were provided with a professional development program, which included an introduction to content through direct teaching, opportunities for practice during classroom routines, and individualized coaching with feedback. Baseline book reading sessions resulted in consistently low levels of educator intervention fidelity based on fidelity checklists, followed by immediate increases in fidelity upon introduction to the program. Students showed receptive vocabulary gains for words targeted during intervention and maintenance sessions. Educators found the program to be feasible for classroom use, and they planned to continue using the targeted strategies in the future. Implications and directions for future research are discussed. (author abstract)