The present study used a randomized control trial to examine the effects of a widely-used multi-component Tier 2 type intervention, Passport to Literacy, on the reading ability of 221 fourth graders who initially scored at or below the 30th percentile in reading comprehension. Intervention was provided by research staff to groups of 4-7 students for 30 min, 4 days a week throughout the school year (M = 90.45 lessons). Tier 1 instruction was observed to be of generally high quality and intervention fidelity was strong. Findings revealed small, average effects (ES = 0.14 -0.28) in favor of intervention students on standardized measures of comprehension, but no effects on word reading or fluency measures. Exploratory analyses indicated intervention effects may differ by students' comprehension abilities. Implications for intervention implementation and directions for future research are discussed. [This paper was published in "Journal of Research on Educational Effectiveness" (EJ1115336).]