Students with non-apparent, high-incidence disabilities encounter barriers in postsecondary STEM learning environments. These barriers negatively influence their success therein. Using Fishkin's (2014) theory of bottlenecks within opportunity structures, data from 16 qualitative interviews show how barriers encountered serve to constrain the success of students with disabilities. These barriers exist during the transition to postsecondary STEM learning environments, and arise from peer and faculty behavior, organizational structures, and the alignment of STEM and disability identity. Major implications relate to the redesign of STEM learning environments and the use of bottlenecks as analytic lens for studying the experiences of students with disabilities.