This article reports on an empirical study that investigated the relative predictive powers of metacognitive awareness of reading strategies, L2 lexical knowledge (depth and breadth combined), and syntactic knowledge for reading comprehension performance in English as a foreign language (EFL) context across two language proficiency levels in Iran. Participants comprised 177 Iranian EFL university students (82 males, 95 females; mean age = 19.17 years; SD = 1.829). The results produced from multiple regression analysis revealed that vocabulary, syntax, and metacognitive strategies can collectively predict 0.88 of changes in reading comprehension. More specifically, vocabulary, syntax, and metacognitive strategies each can predict 0.54 (t = 5.56, p = 0.001), 0.33 (t = 2.66, p = 0.008) and 0.15 (t = 1.96, p = 0.05) of variance in reading comprehension respectively. However, as for the moderation effect of language proficiency on the predictive power of the three variables for reading comprehension, it turned out that it moderated the predictive power of vocabulary knowledge for reading comprehension performance in a significant way. Results are discussed considering the relevant literature.
