We examined the efficacy of 20 weeks of individual supplemental phonics-based instruction for language minority (LM) and non-LM first graders. Students were designated LM if the primary home language was not English (otherwise non-LM). Those performing in the bottom half of their classroom LM/non-LM group in letter knowledge and phonological awareness were randomly assigned to treatment and control conditions. Treatment included alphabetics, decoding, and oral reading practice. Results showed that treatment students (n = 93) outperformed controls (n = 94) on 5 of the 6 posttests; however, LM students exhibited lower treatment response on passage reading fluency. Pretest word reading did not moderate treatment response, and LM students with greater baseline vocabulary showed greater treatment response on posttest word reading and spelling. (Contains 4 tables and 3 figures.)