Research has demonstrated the positive effects of systematically teaching phonemic awareness and phonics in kindergarten and first grade, but many commonly used reading curricula do not adequately incorporate these foundational skills. In this study, we examined the efficacy of an instructional program ("UFLI Foundations") in foundational reading skills (i.e., phonemic awareness and phonics) with students in kindergarten and first grade. We compared students who received a full year of the instructional program to propensity score matched control students, who received business-as-usual instruction, with a cross-cohort quasi-experimental design. Multilevel modeling results demonstrated that adding instruction in foundational skills increased early literacy skills scores by more than 1.0 standard deviation. Further, we found that students of teachers who taught with greater adherence to the "UFLI Foundations" program had larger effects. Implications and future directions are discussed.