Few evidence-based services exist for people with Autism Spectrum Disorder (ASD) as they transition into adulthood, particularly those that foster appreciation of one's own goals and strengths. We developed a transition service for adults with ASD (without Intellectual Disability), and conducted a randomized controlled trial (RCT) focusing on self-report of Quality of Life and Self-Determination outcomes. Thirty participants aged 18-29 were randomized to immediate or delayed intervention, with 26 participants analyzed after 4 were lost to follow-up. Curriculum was tailored to participants' selfexpressed needs in three areas: social communication, self-determination, and working with others. Groups of four-to-six participants with ASD and two facilitators met weekly for 10 weeks. Positive intervention effects were observed on selfreport of Quality of Life; the intervention group scored on average 2 points higher than the control group, 95% CI [−0.2, 3.9]. Positive effects were also observed on the Self Determination Scale (Interpersonal Cognitive Problem-Solving subdomain), where the intervention group scored 2 points higher than control group 95% CI [0.082, 3.4]. In addition, participants rated skills targeted by the curriculum 6 points higher after versus before intervention, 95% CI [3.7, 8.6]. This was echoed by a subset of parents rating their child's skills as seven points higher after versus before intervention, 95% CI [1, 14].Lay Summary: These findings indicate that it is possible to increase Self-Determination and subjective Quality of Life in adults with ASD through a brief group-format service, and provide a model for doing so. Self-Determination abilities are linked to improved adult outcomes in individuals with other disabilities. These often overlooked factors should be incorporated in programming for adults with ASD as they transition to adulthood.