Approximately 1.2 million autistic youth will reach the legal age of adulthood over the next decade. Given dynamic changes in the socioecological context of the transition to adulthood, we produced an updated transitions research agenda reflecting the perspectives of autistic young adults, care partners (parents), and professionals who use autism research. We conducted 9 focus groups: 4 young adult, 4 care partner, and 1 professional, with 59 total participants. Young adults were grouped by self-reported identity: (1) racial and ethnic minority, (2) lesbian, gay, bisexual, transgender, queer, intersex, asexual, and other identities, and (3) nonspeaking, in addition to a general group. We selected care partners who supported youth with varying intensity of support needs. We used rapid qualitative inquiry methods to extract key points from answers to semistructured interview questions. Delays in diagnosis and transition processes, and placement on wait lists resulted in significant obstacles to successful transitions. Parents assumed a dominant role by coordinating services, navigating systems and identifying opportunities for community participation, and providing direct supports. There was an overarching need for inclusion of autistic people in transitions research and consideration of cultural differences in priorities and values. Participants prioritized investigation of variation in transitions among autistic youth with intersecting identities, navigation support (eg, peer mentors), efficacy of services and supports (eg, transition and employment services), differences in available services by location, and problems within specific benefits programs. Research should focus on understanding population-level factors of system performance on outcomes and support needs, service delivery among marginalized groups, and transformation of complex service ecosystems.