this experimental study has been conducted to test the effect of oral presentation on the development of l2 learners grammar. but this oral presentation is not merely a deductive instruction of grammatical points, in this presentation two hypotheses of krashen (input and low filter hypotheses), stevicks viewpoints on grammar explanation and correction and widdowsons opinion on limited use of l1. are taken into account, the subjects (n60) are divided into two equal groups. experimental group received the oral presentation and control group was given the same grammatical points in gt method. throughout the study, it was tried to find answers to the following research questions: 1- does oral presentation of l2 play a significant role l2 learners development of grammar system? 2- if input is understood and there is enough of it, is the necessary grammar automatically provided? 3- is, at least, some of the grammar instructed through oral presentation, reflected in students oral performance? the results of the statistical procedures proved that oral presentation of l2 plays a significant role in providing l2 learners with grammar development and necessary grammar is automatically provided without resorting to laborious task of explaining detailed rules and exceptions. moreover, it was shown that majority of the students used some of the structures applied in teachers input. null hypothesis was rejected in 0.05 level.