Augmentative and alternative communication (AAC) systems often supplement oral communication for individuals with intellectual and communication disabilities. Research with preschoolers without disabilities has demonstrated that two visual--perceptual factors influence speed and/or accuracy of finding a target: the internal color and spatial organization of symbols. Twelve participants with Down syndrome and 12 with autism spectrum disorders (ASDs) completed two search tasks. In one, the symbols were clustered by internal color; in the other, the identical symbols had no arrangement cue. Visual search was superior in participants with ASDs compared to those with Down syndrome. In both groups, responses were significantly faster when the symbols were clustered by internal color. Construction of aided AAC displays may benefit from attention to their physical and perceptual features.