This paper provides a secondary analysis of the May, Sirinides, Gray, and Goldsworthy (2016) evaluation of the Reading Recovery scale-up. We extend their findings to include analysis of the six subscales of the "Observation Survey (OS) of Early Literacy Achievement" (Clay, 2013) that the What Works Clearinghouse has previously used to access the beginning reading domains of Alphabets, Reading Fluency, and General Reading Ability. We also provide a sub-group analysis of students whose entry scores predict a severe reading difficulty at the end of first grade. This analysis includes the ITBS subscales reported by May et al. for their main analysis. The May et al. design was a randomized controlled trial with independent samples in each of the four years of the study. In total 3444 pairs of first grade students were matched on the fall OS Text Reading Level measure and then randomly assigned to the treatment or control condition. The secondary analysis presents descriptive statistics and Hedges's d effect size calculations for the total sample and sub-group on each of the subscales of the OS. The analysis for the Text Reading Level measure is calculated for both raw scores and scale scores. The scale scores provide an interval measure that is more appropriate for calculations of effect size (D'Agostino, Rodgers, & Mauck, 2018). The results showed medium to large effects on each of the OS measures for the total groups and severely at-risk subgroup. The appendix includes additional tables for each year of the scale-up, demonstrating replication of these findings over the four independent RCTs. The Institute of Education Sciences (IES, 2016) considers its highest evidence level as "an independent evaluation of a fully-developed education intervention with prior evidence of efficacy, when implemented by the end user under routine conditions" (IES, 2016, p.5). The replication of substantial effects on the ITBS and OS subscales demonstrates the ability of the Reading Recovery network to partner with schools to scale-up and implement an effective early intervention.