Recent theories of short-term memory (STM) distinguish between item information, which reflects the temporary activation of long-term representations stored in the language system, and serial-order information, which is encoded in a specific representational system that is independent of the language network. Some studies examining the relationship between reading acquisition and verbal STM for order and item information separately in beginning readers have found that order STM capacity is independently predictive of nonword decoding abilities in first grade, but item STM is not. In this longitudinal study, we first aimed to explore whether this finding also holds for nonword spelling abilities. We also sought to determine whether order STM capacity remains an independent predictor of nonword decoding and spelling abilities in the second year of reading instruction. For this purpose, 70 typically developing children were followed over 3 years, from kindergarten to second grade. In kindergarten, children were administered order and item STM tasks and phonological awareness tasks, in addition to tasks assessing letter name knowledge, vocabulary knowledge, and nonverbal reasoning. In first and second grades, the children's word and nonword reading and spelling abilities were assessed. The results revealed that order STM capacity was a robust independent predictor of nonword reading and spelling abilities in first and second grade, but was not related to the abilities to read and spell words. The specific role of order STM in the acquisition of the sublexical reading and spelling routes is discussed.