Collaborative (Co-)teaching is a complex instructional delivery model used to improve teaching practice in inclusive settings. The model involves multiple certified teachers--representing both special and general education--sharing the same space and presenting material to classrooms with a wide variance in learning needs. Co-teaching has become an increasingly popular form of instructional delivery in school districts attempting to improve Inclusive Education outcomes. It also creates a unique educational space that is often challenging for teachers to navigate and for several reasons, its affordances unfulfilled. This multiyear investigation and intervention uses a Design-Based Research (DBR) approach to understand the environment of a local co-teaching team, co-design supportive tools, and implement those tools to improve practice. This investigation addresses a lack of research attending to the implementation of--and learning involved in--co-teaching practice. Multiple co-teachers participated in this collaborative project over two years. Two novel co-teaching tools were co-constructed: (1) Co-teaching Lesson Guiding and Reflecting Form, "and" (2) Collaborative Teaching and Learning Map. Local implementation of the tools as well as implications to research and practice 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/en-US/products/dissertations/individuals.shtml.]