This study explored the differential effects of task familiarity and task repetition on EFL learners’ writing performance in weblog-based environment and face-to-face classroom. To this end, 87 Iranian intermediate EFL students from two branches of Islamic Azad University, Iran were volunteers for participating in this study. Subsequently, only 60 students out of these 87 students were chosen based on their preliminary English test scores, and were randomly assigned to two groups (30 students in weblog / 30 students in face-to-face). As well, each group was divided into two sub-groups: 15 students in task repetition group, and 15 students in task familiarity group. During the treatment, the task repetition group performed twelve tasks with the same procedure and exactly the same content. The students in the task familiarity group were provided with tasks on different topics for the subsequent sessions. Each session, one of these tasks was familiar (e.g., events in Iran) for the learners and the other one was unfamiliar (e.g., events in France. The results of the Two-way ANOVA revealed that there is no significant difference between the writing performance of Iranian EFL learners receiving task repetition compared to those receiving task familiarity. Besides, the results indicated that the writing scores of learners receiving task repetition through weblog-based environment were better than those in face-to-face classroom. Regarding task familiarity, the results of the Two-way ANOVA showed that there is no statistically significant difference between writing performance of learners who receive task familiarity through weblog-based environment in comparison to those in face-to-face classroom. The findings of this study may have implication for EFL teachers and material developers to pay attention to the contribution of blogging to writing achievement, and develop materials, techniques, and procedures that are suitable for blog oriented writing. پرونده مقاله