The role of the learners’ first language (L1) in learning second language (L2) writing has recently become a focus in SLA research. There have been many studies focusing on different aspects of this phenomenon. The results of these studies have shown how L1 use may play facilitative roles in producing writing in the second language. Many variables, such as task type and language proficiency, have also been studied in this regard. Yet, there seems to be a paucity of research on whether L1 use can significantly improve the quality of written productions in L2. The present study was therefore designed to peruse this question and find what aspects of writing may improve with L1 use. To this end, the written productions of 36 Persian-speaking intermediate English learners writing an argumentative paragraph were analyzed. 6 of the 12 groups were asked to collaborate in their first language and the others were limited to using the second language in their collaborations. The results of statistical comparisons between the first language and second language groups revealed that L1 use can significantly improve the overall score gained by the L2 writers. It was also found that L1 use improves the quality
