This meta-analysis examines the effectiveness of a group of instructional approaches (i.e., cooperative, collaborative, and peer tutoring) at improving literacy outcomes for English language learners. Main effects analyses of a sample of 28 experimental and quasi-experimental studies reveal that peer-mediation is more effective for ELLs than individualized or teacher-centered comparison conditions (g = 0.486, SE = 0.121, p <0.001). A number of potential moderators were examined, and two study quality variables proved significant. Also, grade level was a significant moderator, with middle school students demonstrating much smaller gains than elementary or high school students. Finally, descriptive analysis of moderators provides tentative evidence that ELLs showed greater gains on word-level outcomes than text-level outcomes and that interventions for which peer-mediation was one of several tightly-woven components were twice as effective as interventions utilizing peer-mediation alone.