This study used data from the National Longitudinal Transition Study 2012 (NLTS 2012) to explore the individualized education program (IEP)/transition planning participation and role of students with the most significant cognitive disabilities, compared to students with other disabilities. We viewed students with the most significant cognitive disabilities as those included in three disability categories--"autism, intellectual disability, and multiple disabilities"--who took an alternate assessment. The study also included an analysis of student's participation in relation to their functional, communication, and self-advocacy skills, and student-teacher relationships. Although students with the most significant cognitive disabilities experienced greater limitations overall, students with other disabilities were experiencing similar challenges. Implications for practice were discussed from the lens of student engagement, self-determination, and student's leadership role.