Oral language comprehension (OLC) and vocabulary depth are widely recognized as key predictors of reading comprehension. However, research has either provided a limited representation of OLC or failed to acknowledge the distinctive predictive nature of vocabulary depth. This study investigates the combined contributions of OLC, conceptualized as a unified composite of foundational language variables and compares its effects on reading comprehension to vocabulary depth, while accounting for writing abilities. A total of 169 advanced Korean university EFL students were tested on listening comprehension, grammar knowledge, vocabulary breadth, vocabulary depth, and reading comprehension in English. SEM analyses revealed that both OLC and vocabulary depth made unique contributions to reading comprehension, with OLC demonstrating relatively stronger predictive power. Writing abilities did not show significant effects when OLC and vocabulary depth were considered in the same model. These findings underscore the independent predictive roles of OLC and vocabulary depth in L2 reading comprehension and highlight the importance of integrating these constructs into EFL pedagogical practices.