A critical component of effective communication is the ability to consider the knowledge state of one’s audience, yet individuals with autism spectrum disorders (ASD) have difficulty representing the mental states of others. In the present study, youth with high-functioning ASD were trained to consider their reader’s knowledge states in their compositions using a novel computer-based task. After two training trials, participants who received visual feedback from a confederate demonstrated significantly greater communicative clarity on the training measure compared to a control group. The improvements from training transferred to similar and very different tasks, and were maintained approximately 6 weeks post-intervention. These results provide support for the sustained efficacy of a rapid and motivating communication intervention for youth with high-functioning ASD.