In every region in the world people are working to close the gap of unmet need for AT, and to open the gate to quality AT products and services. Capturing the outcomes of assistive technology (AT) is essential to know what works and what not. But efforts often are not co-ordinated: different terminology is used and different measures and lack systems to enable AT professionals and users to share knowledge and demonstrate effectiveness for policy makers and resource allocation. The Global Alliance of AT Organisations, GAATO, have brought global stakeholders together to articulate challenges related to outcome and impact measurement as a first step to finding solutions. Over 300 AT stakeholders across all global regions took part in a collaborative consensus building process coordinated by Emma Smith, Natasha Layton, Roger O. Smith, Silvana Contepomi, and Esther Dakin-Poole, to identify the AT Outcomes and Impacts Grand Challenges of our time. During the session we will present GAATO, the innovative methodology used, the extensive dataset gathered, and the results of the Grand Challenge process which will inform research, support systemic advocacy for better AT policy, and give voice to many hundreds of AT stakeholders from across the globe. Experts will comment on the findings and the audience will be involved in a discussion on the next steps.