Vocabulary knowledge at school entry is a robust predictor of later reading achievement. Many children begin formal reading instruction at a significant disadvantage due to low levels of vocabulary. Until recently, relatively few research studies examined the efficacy of vocabulary interventions for children in the early primary grades (e.g., before fourth grade), and even fewer addressed vocabulary intervention for students at increased risk for reading failure. In more recent work, researchers have begun to explore ways in which to diminish the "meaningful differences" in language achievement noted among children as they enter formal schooling. This article provides a review of a particularly effective model of vocabulary intervention based on shared storybook reading and situates this model in a context of tiered intervention, an emerging model of instructional design in the field of special education. In addition, we describe a quasi-experimental posttest-only study that examines the feasibility and effectiveness of the model for first-grade students. Participants were 224 first-grade students of whom 98 were identified as at risk for reading disability based on low levels of vocabulary. Results of a multivariate analysis of variance revealed significant differences on measures of target vocabulary knowledge at the receptive and context level, suggesting that students at risk for reading failure benefit significantly from a second tier of vocabulary instruction. Implications for classroom practice as well as future research are provided.