Hossein Mohammadzadeh - Department of English Language Teaching, Tabriz Branch , Islamic Azad University, Tabriz, Iran.
Nasser Ghafoori - Department of English Language Teaching, Tabriz Branch, Islamic Azad University, Tabriz, Iran
Mahnaz Saeidi - Department of English Language Teaching, Tabriz Branch, Islamic Azad University, Tabriz, Iran

The current study was an attempt to investigate the impact of grouping type on the grammatical accuracy of Iranian EFL learners in collaborative writing. Through administering the Michigan Test of English Language Proficiency, ۶۴ female university students available participated in this study and were assigned to two groups--heterogeneous and homogeneous. The treatment process lasted ۱۲ weeks of collaborative writing and revising, with emphesis on the development of the the participants’ written grammatical accuracy. They were pretested and posttested through a descriptive free writing measure. The results revealed that the participants in both groups had higher posttest scores. Using ANCOVA, it was found that there was a differential effect of grouping type on the grammatical accuracy of homogeneous and heterogeneous pairs, indicating that the participants in heterogeneous group had significantly higher posttest scores than those in homogeneous group. Furthermore, although the grammatical accuracy of both groups increased, a significant difference was observed between them, revealing that the participants in heterogeneous group outperformed those in homogeneous group. The findings of this study can be interpreted in terms of the sociocultural theory and Vygotsky’s idea of the zone of proximal development.

Collaborative Writing, grouping type, homogeneous group, heterogeneous group, Grammatical Accuracy