Educators and researchers agree that oral language is fundamental to students' reading acquisition. It is not clear how best to conceptualise oral language within models of reading -- as one's overall understanding of spoken language, or as individual skills, each with unique contributions to children's reading comprehension. In our longitudinal study of children in Grades 2 and 3, we examined the unique contributions of three oral language skills -- vocabulary, syntactic awareness, and morphological awareness -- to gains in reading comprehension assessed later that academic year (N = 116) and in the spring of the following academic year (N = 87). In our most conservative analyses, we controlled for children's listening comprehension in addition to prior reading achievement. Each language skill predicted variance in later reading comprehension beyond that accounted for by initial word reading and reading comprehension. In analyses with listening comprehension also controlled, each of syntactic awareness and morphological awareness retained their predictive power. Morphological awareness emerged as the most robust predictor and was associated with greater increases in reading comprehension for students in third versus second grade. Results support theoretical models that identify and differentiate contributions from individual oral language skills to reading comprehension. Our findings suggest that increasing each of these oral language skills within the elementary classroom may lead to advances in children's reading comprehension.