The purpose of the present study was to see which one of the two instruction-processing instruction (PI) and meaningful output based instruction (MOBI) accompany with prompt and recast- is more effective on EFL learners’ writing accuracy. To fulfill the purpose of the study, a sample of 74 intermediate students of one of the language school of Iran sat for a standardized sample of PET English Testing (PET). Sixty students whose score fell one standard deviation above and below the mean were selected and randomly divided into two equal groups. One group was taught and practiced processing instruction (PI) and the other group received meaningful output-based instruction (MOBI) and did not practice processing strategies. Before starting any treatment a free-writing was administrated at first phase of instruction as a pre test. Moreover, at the final phase a free writing posttest was administered too among the students in both groups in order to see if there is any significant difference between their writing accuracy. The pretest and posttest required the subjects to use three English tenses (simple present, simple past, future) in their writing. The mean scores of both groups on the pre test and post test were compared through a t-test. The results of the pretest showed that there was not any significant difference between two groups. The result of posttest led to the rejection of the null hypothesis, implying that PI had a significantly more effect on writing accuracy. These results suggested that, although processing instruction appears to be more effective, output-based instruction as well as processing instruction can lead to linguistic development. The findings of this study have implications not only for both EFL learners and teachers but also for EFL textbook writers.