This study investigated the possible effect of collaborative dialogue on reading comprehension improvement of Iranian intermediate EFL learners. Furthermore, the current study examined the difference between the effectiveness of collaborative dialogue in co-equal and expert peer groups on reading comprehension improvement of intermediate EFL learners. To this end, 90 intermediate female EFL learners were divided into two experimental groups and one control group. The expert peer(s) in the first experimental group helped coequals through collaborative dialogue in doing reading tasks. On the other hand, the participants of the second experimental group assisted their coequals through collaborative dialogue in doing the reading tasks and the subjects of the third group worked individually. To answer the research questions, three Kruskall Wallis Tests, three Wilcoxon Signe Rank Tests, and three Mann-Whitney U Tests (post-hoc) were used. The data obtained showed that collaborative dialogue in groups including expert peer was the most effective procedure for the intermediate EFL learners reading comprehension development. Moreover, although reading comprehension development of co-equal peers, in average, was more than participants of control group, this improvement was not significant.
