This study examined the effect of collaborative peer- and teacher-scaffolding on Iranian EFL learners' intentional and incidental grammar learning in writing at Bu-Ali Sina University, Hamedan. 18 students took part in the study, all were in term 2, studying English Translation. There were 11 collaboration episodes in each of which, there was a scaffolder, a scaffoldee and the teacher (the first researchers). The first five groups were the intentional group and episodes 6, 7, 9, 10, and 11 were the incidental group. The student in episode 8 had no errors in her essay. There were three topics to choose from and the subjects were asked to write an essay about one of them. Then, each student was given an essay in order to take it home and correct it. Based on Aljaafreh and Lantolf's (1994) Regulatory Scale, the scaffolders were asked to correct their classmates' errors/mistakes, within their ‘zone of proximal development’ (ZPD). Whenever needed, the researcher entered the collaborations. For transcription and further analyses, the collaborations were tape-recorded. The results for both the intentional and the incidental groups showed a significant improvement in the subjects’ performance in the test. That is, they were all able to appropriate the grammatical points they had not known prior to the collaborations. However, there was no significant difference between the intentional group and the incidental group.
