ABSTRACT The purpose of this study was to systematically review the components of oral language (OL) instruction and meta-analyze the effects of OL instruction on vocabulary and listening comprehension (LC) skills. We included experimental and quasi-experimental studies with 3- to 6-year-old children at risk for reading difficulties based on economic disadvantage or poor performance on OL assessments. Additionally, included studies had to report using at least one vocabulary or LC outcome measure. From the 16 eligible studies, we computed 80 standardized mean differences (SMDs), ranging from 2 to 14 SMDs per study (Mdn = 4). The multivariate weighted average SMD with robust variance yielded a positive effect of 0.52 (95% CI = 0.29 – 0.76), indicating OL instruction significantly improved children’s vocabulary and LC. Although measure type, intervention session length and frequency, and publication type were explored as moderators, only outcome skill and measure type were significant. Findings suggest it is feasible for classroom teachers to implement effective OL practices.