A study involving 75 Spanish-speaking fifth graders from a school in the Chicago area investigated whether a peer-led, open-format discussion approach, known as Collaborative Reasoning, would accelerate the students' English language development. Results showed that, after participating in eight discussions over a four-week period, the CR group performed significantly better than the control group on measures of listening and reading comprehension. The CR group produced more coherent narratives in a storytelling task. The reflective essays written by the CR group were longer; contained more diverse vocabulary; and contained a significantly greater number of satisfactory reasons, counterarguments, and uses of text evidence. CR discussions also enhanced students' interest and engagement in discussions, perceived benefits from discussions, and attitudes toward learning English. (Contains 6 tables and 1 figure.)