Researchers in 2 studies investigated the effectiveness of a general education/special education collaborative teaming process in increasing the engagement, development, and learning of preschoolers with severe disabilities who were placed in general education early childhood programs that operated under a team-teaching model. The process included monthly team meetings to develop educational and social supports for targeted preschoolers, which were then collaboratively implemented by the educational team members. Study 1 focused on 3 teams composed of early childhood and special education teachers, instructional assistants, speech-language therapists, and parents who supported a child with significant disabilities attending one of the 3 participating preschools. Study 2 extended the collaborative teaming model to include all preschoolers with disabilities attending one of the preschool programs from the first study who required intensive levels of support (4 children). The effectiveness of the collaborative development and implementation of support plans -- and the extent to which the collaborative teaming process was judged to be natural to the existing classroom culture and useful in producing positive child outcomes --was evaluated in both studies.