Autistic people who cannot speak risk being underestimated. Their inability to speak, along with other unconventional behaviors and mannerisms, can give rise to limiting assumptions about their capacities, including their capacity to acquire literacy. In this preregistered study, we developed a task to investigate whether autistic adolescents and adults with limited or no phrase speech (N = 31) have learned English orthographic conventions. Participants played a game that involved tapping sequentially pulsing targets on an iPad as quickly as they could. Three patterns in their response times suggest they know how to spell: (a) They were faster to tap letters of the alphabet that pulsed in sequences that spelled sentences than letters or nonsense symbols that pulsed in closely matched but meaningless sequences; (b) they responded more quickly to pairs of letters in meaningful sequences the more often the letters co-occur in English; and (c) they spontaneously paused before tapping the first pulsing letter of a new word. These findings suggest that nonspeaking autistic people can acquire foundational literacy skills. With appropriate instruction and support, it might be possible to harness these skills to provide nonspeaking autistic people access to written forms of communication as an alternative to speech.