Iranian high school students confront various challenges in understanding reading passages and learning vocabulary since appropriate process-oriented assessment techniques with constructive and communicative feedback are not practiced to consolidate instruction and learning. The effect of formative assessment (FA) retelling strategy on vocabulary knowledge and understanding passages was investigated and scrutinized in this quasi-experimental study in the EFL context. Thus, a sample of 48 intermediate EFL students was selected and assigned to two intact groups. The retelling assessment was implemented for the experimental group (EG), while the product-oriented summative assessment was applied to the control group (CG). The pre-test scores were taken at the first phase of the study followed by the eight-week assessment process. Finally, the post-test scores were taken. For the purpose of the analysis, the Independent Samples T-test and the one-way ANCOVA were utilized to compare and contrast the mean scores. The findings were in favor of the retelling technique which developed the vocabulary command and text comprehension in the EG. Moreover, little or no significant impact was revealed for the product-oriented assessment in the CG. The findings can be pedagogically rewarding for learners, teachers and theoreticians and may cast light on SLA research in applying FA techniques.
