The research project “Cooperation for Inclusion in Educational Transition”, funded by the Austrian Science Fund (FWF) (project number: P-29291-G29; project-leader: Helga Fasching) at the Department of Education in Vienna, focuses on participatory cooperation/collaboration. Missing or lacking cooperation/collaboration between the adolescents with disabilities, his or her parents and the support providers in- and outside school is one of the various barriers youths with disabilities are confronted with. The importance of cooperation/collaboration has already been identified as a relevant determinant and is internationally considered as an important key factor in fostering transition processes (Fasching 2012; Todd 2007). Nevertheless, to date, the international and national research community has not taken into sufficient consideration the topic of participant cooperation/collaboration in the transition of persons with disabilities, especially not with respect to diversity. The funded research project can contribute to close the gap and provide important information about how adolescents with disabilities, their parents and professionals in Austria experience the transition process. To gain a deeper insight into the experiences of the individuals the main research question is as follows: What are the experiences of pupils with disabilities and their parents/families with cooperation/collaboration with professionals in the period of transition from SEC I to SEC II or employment? The project is framed as a qualitatively-driven mixed-methods study, with the main focus lying on qualitative methods (interviews and observations), and is assigned to the basic exploratory research. Based on the (constructivist) Grounded Theory according to Kathy Charmaz (2014) case studies are used in a longitudinal approach to examine how the individual actors (adolescent with disability, his/her parent and the professionals) cooperation/collaboration with each another. As part of the presentation we´ll present and discuss the concept underlying the research project (design, methods and theoretical framework). We will give an insight in current project activities and focus on arising issues and challenges concerning participative cooperation/collaboration. We are interested in sharing experiences on transitions and transition research and open up for cross-country-discussion.