This experimental study was designed to validate a short-term supplemental reading intervention for at-risk first-grade children. Although substantial research on long-term supplemental reading interventions exists, less is known about short-term interventions. Thirty first-grade children were randomly assigned to intervention or control conditions. Students in the intervention received 16 hours of instruction. Analyses of pre- and posttest data and growth measures suggest that short-term supplemental reading intervention had a significant effect on children's reading skills; however, effects were not consistent across measures. Parent and teacher ratings moderated significant effects. Findings support the validity of a brief intervention for students at risk for reading failure that may inform Tier 2 interventions within a Response to Intervention framework. (Contains 9 tables and 2 figures.)