The goal of this research was to highlight the role social regulatory processes play in making students' teamwork in reciprocal teaching (RT) groups (a classroom activity in which students take the teacher's role in small group reading sessions) effective. In addition to teamwork quality, we expected peer feedback to be a key factor in enhancing students' reading comprehension achievements. Because previous research (Schünemann et al. in "Contemp Educ Psychol" 38:289-305, 2013) has shown that procedures of self-regulated learning (SRL) augment the effects of RT methods, we further assumed that such procedures would promote the quality of students' collaborative efforts. In a cluster-randomized trial, students in 12 fifth-grade classes practiced a strategic approach to reading either in a RT condition or in a RT + SRL condition. In one of the 14 sessions, students' interactive behavior was videotaped. Strategy use and reading comprehension were assessed at pretest, posttest, and maintenance. Performance differences between conditions were reliable only at maintenance. A multilevel mediation analysis showed that relative to RT students, RT + SRL students were better able to provide their teammates with informative feedback and organize their group work in a task-focused manner. Only feedback quality mediated the sustainability of treatment effects on strategy use and reading comprehension. In essence, this research suggests that effective reading comprehension trainings should integrate explicit instruction and practice in reading strategies, SRL, and focus on supportive peer processes in small groups with extensive instruction and practice in peer feedback.