Of the 50,000 youth with Autism Spectrum Disorder (ASD) who achieve adulthood each year, the National Autism Indicators Report disclosed that 36% attend a postsecondary school. Among these, an 80% majority, attended 2-year colleges and 11% attended 4-year colleges (Roux et al., 2015a, 2015b). A systematic review of the literature exposed a gap with respect to the participation of parents of postsecondary students with ASD, a best practice in primary and secondary education. To understand parent participation in the postsecondary education of their students with ASD, I designed a mixed-methods research study examining three domains of support, autonomy, social integration, and stress/emotional relief. An online dichotomous survey of 45 questions plus 14 open-ended questions collected data contemporaneously from 45 parents. Construct validity as measured through Mokken Scale Analysis rated strongest for social integration with the scalability coefficient H=0.39 and standard error of 0.08, with KR-20 analysis confirming high reliability of 0.76 for internal consistency. Quantitative and qualitative results triangulated, with academic and executive function support emerging as additional domains of participation exposed through qualitative elaboration. To generalize, parents were fostering skills which fall under the rubric of self-determination, the development of which is delayed beyond young adulthood among individuals with ASD, particularly skills associated with executive function. Further testing of the dichotomous instrument with larger sample sizes is warranted and suggested. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com.bibliotheek.ehb.be/en-US/products/dissertations/individuals.shtml.]