In the written texts on foreign language learning, a group of studies has stressed the function of learning context and learning chances for learners’ language input. The present thesis had two main goals: on the one hand, different types of input to which Iranian grade four high school EFL learners’ are exposed were looked at; on the other hand, the possible relationship between types and quantity of input and Iranian EFL learners’ oral proficiency was investigated. It was supposed that EFL learners who have access to more input will show better oral proficiency than those who do not have. Instruments used in the present study for the purpose of data collation included PET test, researcher- made questionnaire, oral language proficiency test and face- to -face interview. Data were gathered from 50 Iranian female grade four high school foreign language learners who were selected from among 120 students whose score on PET test were + 1SD from the mean score. The results of the Spearman rank –order correlation test for the types of input and oral language proficiency scores, showed that the participants’ oral proficiency score significantly correlated with the intended four sources of input including spoken (rho= 0.416, sig=0.003), written (rho= 0.364, sig=0.009), aural (rho= 0.343, sig=0.015) and visual or audio-visual types of input (rho= 0.47, sig=0.00). The findings of Spearman rank –order correlation test for the quantity of input and oral language proficiency scores also showed a significant relationship between quantity of input and oral language proficiency (rho= 0.543, sig= 0.00). The findings showed that EFL learners’ oral proficiency is significantly correlated with efficient and effective input. The findings may also suggest answers to the question why most Iranian English learners fail to speak English fluently, which might be due to lack of effective input. This may emphasize the importance of the types and quantity of input in EFL classes and syllabus designers.