Reading acquisition involves learning to associate visual symbols with spoken language. Multiple lines of evidence indicate that instruction on the relationship between spellings and sounds may be particularly important. However, it is unclear whether the effectiveness of this form of instruction depends on pre-existing oral language knowledge. To investigate this issue, we developed a series of computational models of reading incorporating orthographic, phonological and semantic processing to simulate both artificial and natural orthographic learning conditions in adults and children. We exposed the models to instruction focused on spelling-sound or spelling-meaning relationships, and tested the influence of the models’ oral language proficiency on the effectiveness of these training regimes. Overall, the simulations indicated that oral language proficiency is a vital foundation for reading acquisition, and may modulate the effectiveness of reading instruction. These results provide a computational basis for the Simple View of Reading, and emphasise the importance of both oral language knowledge and spelling-sound instruction in the initial stages of learning to read.