Background: There is a paucity of research into interventions that help people with intellectual disabilities learn to read. This feasibility study examines whether an online reading programme, Headsprout, with additional support strategies and supervision (the intervention), can be delivered by support workers/family carers and the feasibility of conducting a later large-scale effectiveness trial. Methods: The study used a 2-arm randomised controlled trial (RCT) design with an embedded process evaluation using a mixed methods approach. Results: Thirty-six adults with intellectual disabilities were recruited. Informed consent and data were obtained remotely. Progression criteria for recruitment, retention, randomisation and usual practice were met; intervention adherence and fidelity were poor. Pressure on support services was a key barrier. Conclusions: Whilst progression to a large-scale effectiveness trial was not recommended, the success of conducting an RCT and remotely obtaining informed consent and data from adults with intellectual disabilities opens opportunities for increased participation in research for a currently under-represented group.