The purpose of this study was to investigate how brief experimental analyses (BEAs) could be used to identify effective interventions for Kindergartners (2 girls and 2 boys, 5 years and 7-10 months old) with low performance and/or growth slope in letter sound fluency (LSF). Interventions were tested within a multielement design with brief mini-reversals until an intervention yielding at least 20% improvement on a specific subskill measure or a curriculum-based measure of LSF was identified. BEA-identified interventions were implemented one-on-one for 5 to 9 weeks. A multiple-baseline design across participants showed large intervention effects (average adjusted d = 2.4) on general outcome measures, supporting treatment validity of BEAs. Findings extend the BEA literature to younger participants, early reading interventions, and early reading measures. (Contains 1 table and 9 figures.)