Children with partially intelligible speech and language difficulties are often provided with speech-generating devices (SGDs) to support their spoken communication. However, little is known about how SGDs can be used best to facilitate language development. This study evaluated the effects of a conversation-based intervention using SGDs, on the rate of expressive clause production in children with speech that is partially intelligible (SPI). A multiple probe across participants design was used to evaluate intervention with four children aged 8 to 10 years. Following baseline monitoring, the children received language-focused intervention involving adult recasting, SGD modeling, and prompting to repair. Participants showed increases in their rate, complexity and length of clause use. Gains were sustained and generalized. Intervention using conversation, recasting, and SGD modeling can increase clause production and grammaticality of children with SPI.