Inclusive education is generally conceptualized as "access" to learning opportunities, "participation" with typically-developing peers and adults, and systems-level "supports" (Division for Early Childhood [DEC] & National Association for the Education of Young Children [NAEYC], 2009). This definition has become the cornerstone for efforts to support teachers' practice (Barton & Smith, 2015a; Odom, Buysse, & Soukakou, 2011) and federal efforts to advance high-quality inclusive education (U.S. Department of Health and Human Services & U.S. Department of Education, 2015). Yet, research has inconsistently taken up this definition, instead, positioning any classroom with both children with and without disabilities as inclusive (e.g., Hardiman, Guerin, & Fitzsimons, 2009; Nahimas, Kase, & Mandell, 2014; Pelatti, Dynia, Logan, Justice, & Kaderavek, 2016; Rafferty, Piscitelli, & Boettcher, 2003). Additionally, the rapid increase in early childhood education (ECE) programs has created a patchwork early education system with differences based on funding sources, attendance eligibility criteria, teaching and staffing patterns, and program standards, among other features (Guralnick & Bruder, 2016). Consequently, children with disabilities may be included into a variety of different types of early childhood settings that differ based on their classroom's organizational context and service delivery models (Odom et al., 1999). More research is needed to understand how the three core features of inclusive education (access, participation, supports) may differ across different types of early childhood settings. Such information would allow the field to differentially support programs to facilitate high-quality inclusive education for young children with developmental delays or disabilities. The present dissertation study aimed to add to the literature regarding the influence of contextual features (i.e., organizational context, service delivery model) on the quality of children's inclusive education and their individual classroom experiences. The study was conceptually grounded in bioecological systems theory (Bronfenbrenner, 1994; Bronfenbrenner & Morris, 2006), the DEC and NAEYC (2009) definition of inclusive education, and the inclusion models categorization put forth by Odom and colleagues (1999). The study used a sequential explanatory mixed methods design (Creswell & Plano Clark, 2011; Ivankova, Creswell, & Stick, 2006) and embedded, multiple case study method of inquiry (Yin, 2014). Seven classrooms across four programs participated, including 12 children with disabilities and nine children without disabilities who participated as focus children. The classrooms represented three inclusion models: Co-teaching classrooms within the public school setting, early childhood special education (ECSE) classrooms within the public school setting, and early childhood education (ECE) classrooms within a community-based center. The Classrooms Assessment Scoring System (CLASS) and the Inclusive Classroom Profile (ICP) were used as classroom-level measures of global and inclusion quality, respectively. Additionally, the Classroom Code for Interactive Recording of Children's Learning Environments (CIRCLE) served as a child-level measure of children's individual classroom experiences. Finally, 11 classroom teachers and four program administrators participated in interviews to provide their perspectives on implementing inclusive education within their contexts. Findings revealed multiple differences between organizational contexts and service delivery models. Organizational contexts appeared to differ in the extent to which teachers provided academic content aligned with early learning standards, how much teachers incorporated child-initiated activities, and teachers' progress monitoring practices. Service delivery models appeared to differ in teachers' feedback practices for children with and without disabilities, teachers' facilitation of peer interactions, and the ways teachers taught academic content. Programs' differential approaches to the general education curriculum, lesson planning processes, and teacher feedback mechanisms appeared to influence the contextual differences that were observed. Findings provide evidence that early childhood settings do indeed differ in their strengths and needs related to providing high-quality inclusive education. Additionally, findings have significant implications for future research on inclusive education. By examining inclusive education across multiple contexts using a mixed methods approach, this exploratory study contributes a new perspective about how high-quality inclusive education may be supported in context-specific ways. [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://bibliotheek.ehb.be:2222/en-US/products/dissertations/individuals.shtml.]