In their study of English as a Second or as a foreign Language, students learn that some adjectives can be used to modify a subject in a sentence. So, they must be very careful in using the adjectives in correct order in the sentence. Because there is the issue of wrong ordering of adjectives, learners of English as a Second Language well must learn the standard order of adjectives in English language such as articles, judgment, size, shape, age, color, nationality , material, purpose, etc. This study aimed at investigating the interference of L1 (Persian) syntactic structures on L2 (English) Order of Prenominal Adjectives amongst Iranian learners of English. The focus of the study was on the errors committed by Iranian EFL learners in using one special order within simple sentence structure. To find out the impact of their L1 adjective order on their L2 choice of adjectival structures, the errors committed by two groups of EFL learners were investigated. To achieve these objectives, a multiple-choice test was utilized in this study. The findings of the study suggest that the subjects committed a total of 360 interlingual errors with respect to English sentences adjective order. Based on these findings, pedagogical implications such as the major causes of such errors in classroom and communication contexts for language instructors and material designers are discussed. This way, useful and applicable decisions to detect these errors and erroneous structures can be made so that the percentages of errors in this specific case of English structure can be reduced. The implications for material developers are mostly to draw their attention toward designing more tasked-based course books for Iranian English learners, so that this approach becomes the dominant one in teaching contexts and classrooms .The findings also suggested that instructing the adjective order of English using some task-based practices such as role playing and accomplishing some tasks in the form of real life scenarios would help learners accomplish the objectives of learning English grammar.
Keywords: Adjectives order, Interference, Interlingual, Prenominal, task-based practices