Across the United States, State Education Agencies (SEAs) are using tiered strategies, such as Multi-Tiered System of Supports (MTSS) frameworks, to ensure that all students, including diverse learners, receive equal, high-quality education. However, little is known about the extent to which SEAs are encouraging use of MTSS to address the needs of students with moderate-to-severe cognitive disabilities. The present study aimed to examine how SEAs conceptualize and support the implementation of MTSS as an approach to inclusionary education. Data were collected through interviews with key informants in SEAs across 19 states. Members of the research team identified and coded portions of interview transcripts that related to legal requirements for MTSS at the state level, local control as an enabler of or impediment to states' MTSS work, and levels of inclusiveness in MTSS provisions. Three criteria emerged as important to MTSS inclusiveness: (1) inclusiveness in the espoused MTSS scope; (2) extensiveness of inclusive MTSS practices; and (3) specific application of MTSS to students with significant cognitive disabilities. Analyses showed variability across states regarding their commitment to an MTSS approach across the three domains of inclusiveness. Findings showed the value of developing and disseminating MTSS models offering tiered support for all students and the need for SEA offices to engage in collaborative efforts to support the implementation of inclusive MTSS models. The study also raised questions about the role of rhetoric (i.e., "All means all") in promoting or hindering increased inclusiveness in MTSS implementation.