Writing is considered a very complicated task for many EFL students and Iranian EFL learners have many problems in this regard. Present study through a mixed method design, attempted to investigate the effect of Structured Collaborative (SC) pre-writing task versus Unstructured Collaborative (USC) pre-writing task on the writing ability of Iranian EFL students. Among a population of 300 freshmen learners of English language translation of Islamic Azad University, 169 students were selected based on criterion sampling. The criteria for selecting the sample were English language proficiency of the learners, age of the participants and major of their study. On the other hand, 30 teachers were selected based on convenience sampling for the interview part of the study. Then the students were assigned to Unstructured Collaborative (USC), and Structured Collaborative (SC) pre-writing groups. These two clusters were considered as experimental group and as control group. The study was implemented over a period of 16 weeks and involved pre and post-tests. Results of the quantitative data analysis shows that students’ writing proficiency in both groups were improved. However, the outcomes of the study reveals that the (USC) group outperformed the (SC) group. The qualitative data analysis through classroom observation and teachers interview reveals that teachers of (IAU) practiced the collaborative tasks at the three stages of writing in their classes and they also favored and applied the five components of Cooperative Learning (CL). In this study, the researchers took the initiative to make a distinction between structured and unstructured collaborative pre-writing tasks. Consequently, the results of the current study are of benefit for several groups of people, namely language practitioners, university students and educational administrators.

对于许多EFL学生而言，写作被认为是一项非常复杂的任务，伊朗EFL学习者在这方面存在许多问题。本研究通过混合方法设计，试图研究结构化协作（SC）预写作任务与非结构化协作（USC）预写作任务对伊朗EFL学生写作能力的影响。在伊斯兰阿扎德大学（Islamic Azad University）的300名新生英语翻译学习者中，根据标准抽样选出了169名学生。选择样本的标准是学习者的英语水平，参与者的年龄和研究专业。另一方面，根据方便抽样选择了30名教师作为研究的访谈部分。然后将学生分配到非结构化协作（USC），和结构化协作（SC）预编写小组。将这两个簇视为实验组和对照组。这项研究历时16周，涉及前后测试。定量数据分析结果表明，两组学生的写作水平都有所提高。但是，研究结果表明（USC）组优于（SC）组。通过课堂观察和教师访谈进行的定性数据分析表明，（IAU）的教师在课堂上的三个写作阶段中练习了协作任务，他们也偏爱并应用了合作学习（CL）的五个组成部分。在这项研究中，研究人员主动区分结构化和非结构化协作式预写任务。所以，