Brief experimental analyses (BEA) have been primarily used to evaluate the effects of interventional variables on reading fluency deficits. This study expanded this area of research by examining spelling interventions for students with below grade level spelling achievement. Researchers analyzed interventions addressing motivation, practice opportunities, and two instructional interventions. Researchers tested each intervention 3–6 times during the BEA. The two best interventions were applied in an extended treatment analysis and compared to a treatment-as-usual (TAU) condition. During the extended analysis, BEA-identified effective interventions produced the largest number of words spelled correctly as compared to TAU. The current study suggests that (a) a BEA of spelling deficits can be used to identify why a child experiences spelling deficits and corresponding effective interventions, (b) interventions identified in this BEA predict long-term intervention success, and (c) long-term intervention success can be predicted after just one BEA session.