The main concern of most researchers in the field of second and foreign language teaching is lessening the problems and eliminating the hinders on the way of learning a language. Writing is considered as one of the most challenging and complicated tasks for learners to perform particularly when they have to write in a second or foreign language. Numerous studies were done on the importance of the pre-writing stage and activities which are directly and indirectly related to the theme of the writing. Accordingly, the main aim of this study was to examine the effects of group discussion as a pre- activity task on writing ability. To this aim, 27 Iranian EFL learners, who were at the same level –intermediate- studying at Shokuh and Safir Institutes, Birjand, Iran were chosen randomly. Two groups- one control and one experimental group- were studied. In control group the conventional method was used in teaching writing, while in experimental group, group discussion pre-activity task was administered. After 16 sessions, the obtained data of the pretests and posttests was analyzed by SPSS software. According to the results, researcher strongly concluded that group discussion has no significant effect on writing ability of Iranian intermediate learners. This study can help teachers and syllabus designers in choosing and applying an effective pre-activity task. Keywords: writing ability, pre-activity task, group discussion, EFL learners