Fifty-eight, college-preparatory twelfth-grade students and their English teacher participated in this study of whether exploratory talk in small groups can help students assimilate new information on complex topics more effectively than can participation in a class discussion or a lecture. Of the three treatments (lecture, class discussion, student-led small-group discussion), the small-group discussion was significantly more effective in improving the students’ knowledge as they prepared to write. Similarly, differences in the quality of analytic, opinion essays (scored for clear thesis and elaboration of ideas) revealed that small-group discussion was consistently superior for both weaker and stronger writers. Data from composing-aloud protocols revealed that following the talk conditions students were better able to remain on task while composing their opinion essays, and that students made significantly fewer negative comments about their essay production. Attitude measures revealed that students preferred the treatments that allowed them to talk when developing their understanding of complex ideas. Results from all data sources converge to indicate that exploratory talk in student-led small groups can provide a powerful means for developing understanding of complex topics and can facilitate writing about these ideas.