Although the ability to speak is often considered a determining factor of learners ability in the target language, research has given scant attention to strategies that can be used to improve this skill. This study aimed to shed light on the speaking strategies that learners use to deal with problems they encounter when using the target language or to improve the quality of their L2 performance. This study deployed the Oral Communication Strategy Inventory (OCSI) developed by Nakatani (2006) to measure the strategies that students use in oral communications. In doing so, adopting the mixed-methods sequential explanatory design, this study investigated the use of speaking strategies of low and high proficiency English as a Foreign Language (EFL) learners in performing speaking tasks. The participants of the study were 23 low and 25 high proficiency students learning English in an institute in Iran. After performing the speaking tasks, the participants filled out the OCSI questionnaire and answered two open-ended questions. The results indicated that low and high proficiency students employ different strategies. While advanced learners used "accuracy-oriented" strategies the most and "message abandonment" strategies the least, "message reduction" strategies and "thinking in English" strategies, respectively, were found to be the most and the least frequently used by elementary learners. The Mann-Whitney U test indicated that of the six speaking strategies, only "message abandonment" and "thinking in English" strategies were found to be significantly different between elementary and advanced English learners. This study contributes in some ways to the understanding of how students' proficiency level relates to their strategy use and provides English teachers with a variety of pedagogical methods to motivate students and enhance their oral production via speaking strategies.