This classroom-based study examined the effect of collective peer scaffolding activity on self-revised as well as new narrative and descriptive paragraphs developed by 32 EFL university students in a paragraph writing course in Iran. Each genre was discussed and practiced every other week and was followed by a collective peer scaffolding session. For each genre, learners were required to develop a 150-word paragraph in two drafts (pre- and post-collective scaffolding activity) and email them to their lecturer within five days before the next sessions were held. During collective scaffolding sessions representative learners were asked to write their paragraphs on board while other students scaffolded solutions to the problems they noticed in the paragraphs written on board. The analyses of the students? pre- and post-collective peer scaffolding drafts and new developed paragraphs revealed that although the activity improved learners? self-revised drafts, its effect on new developed paragraphs was inconclusive.