Individuals who use augmentative and alternative communication (AAC) are often excluded from learning literacy skills that use phonological approaches due to challenges with verbal production of speech sounds. This study was conducted to evaluate the effectiveness of systematic literacy instruction with materials modified to teach letter-sound correspondences (LSC) to pre-adolescent and adolescents with autism spectrum disorders (ASD) with minimal or no speech who use AAC. A single subject design across three letter-sound sets was used, with three individuals with ASD. A total of 12 LSC were targeted in the intervention. During the intervention, the participants were instructed using model, guided, and independent practice trials using low-tech letter tiles followed by two extension activities: letter sorting and initial letter-sound picture books. A functional relationship was established between the LSC intervention and the percent of correct responses on the LSC assessment probes. Very large and large effects sizes were calculated for all participants across the three LSC sets. The study adds to the very limited research base related to phonics instruction for older learners (ages 9 to 18) with ASD, demonstrating that LSC progress can still be made at an older age with systematic instruction.