This study examines the interaction between the fidelity of implementation of a set of research-based strategies--Collaborative Strategic Reading (CSR)--and outcomes for students with mild to moderate disabilities using data from two nonoverlapping studies in middle school language arts and reading classrooms (Study 1) and middle school social studies and science classrooms (Study 2). The authors use a definition of fidelity that includes both the amount of CSR instruction delivered by teachers and the quality of implementation. Although there were no main effects for quality or amount of CSR instruction, in both studies there was an interaction effect between quality of implementation and special education status. The study used a within-groups design and multilevel analyses, and the results demonstrate that higher quality CSR instruction was associated with higher reading outcomes for students with disabilities. This finding was consistent across Study 1 and Study 2. Implications for practice and future research are discussed.