The purpose of this study was to test the efficacy of a Tier 2 standard protocol supplemental intervention designed simultaneously to develop root word vocabulary and reinforce decoding skills being taught to all students in the core beginning reading program with kindergarten Spanish-speaking English learners (ELs). Participating students were drawn from six public elementary schools in the Midwest. Within classrooms, students were randomly assigned to either the supplemental intervention (treatment) or the specified control condition (i.e., used to control for instructional time and consistency). All instruction in both conditions was delivered by paraeducator tutors and occurred in small groups for approximately 20 min a day, 5 days a week, for 20 weeks (October to April). At posttest, treatment students (n = 93) in the experimental condition significantly outperformed controls (n = 92) on a proximal (i.e., linked directly with the instructional focus of the intervention) measure of root word vocabulary (d = 1.04) and word reading (d = 0.69). Treatment students did not significantly outperform controls on a distal (i.e., not linked directly to the instructional focus of the intervention) measure of reading vocabulary (d = 0.38). The results, practical importance, and limitations are discussed. (Contains 3 tables.)