The National Council for the Social Studies recommends high-quality access to academic content in the social studies domains (history, government, economics, and civics) to improve in-school performance and postschool civic and community outcomes for students in K-12 schools. To date, limited research information exists to inform social studies curriculum content and instructional procedures for students with significant intellectual and developmental disabilities (IDD). A consideration of grade-level aligned and high-quality instruction in social studies curriculum domains during the school years may be especially important for students with significant IDD. Information about evidenced ways to provide social studies instruction may help to promote improvements in graduates' postschool civic, employment, and social outcomes. Structured inquiry-based processes, and other instructional methods that teach pivotal problem-solving skills, may especially help to promote improved lifelong outcomes. The research study described in this dissertation examined the effects of an inclusive, peer supported, structured inquiry-based intervention to teach Utah Studies and US history content for three students with significant IDD at a junior high school. A multiple probe across participants design was used to investigate the relationship between the intervention and students' percentages of correct responding to content probes. Study results suggest that the intervention was strongly associated with improvements in students' percentage of correct responses to acquisition probes and that, after repeated practice, students were able to use the inquiry-based process with untaught instructional materials. General education teachers and paraprofessionals found the intervention to be effective and acceptable. Implications for future research, implications for classroom practice, and study limitations are discussed. [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.]