The interaction between a preschool Nature Based Educational (NBE) setting and children with Autism Spectrum Disorder (ASD) prosocial skill building has yet to be studied in-depth, and the potential of NBE settings for this specific diagnosis in early childhood settings has yet to be explored (Wilson, 1994). Understanding the ideal environment for someone with ASD is a critical issue for providing impactful services and schooling, as the core deficit of prosocial skills varies across different environments. Prosocial skills are vital because they affect access to the social and physical environment. This is especially important for kids with ASD who struggle with social skills. By offering an environment that is both sensory friendly and increases low-stakes social interactions, NBE has the potential to be an accessible environment for learning prosocial skills. This research explores the relationship between children with ASD prosocial skill development and NBE using a Descriptive Case Study using Mixed Methods Grounded Theory (MM-GT) with concurrent Triangulation design (Laws, 2023). Qualitative methods are based on constructivist epistemology, and quantitative methods are based on post-positivist epistemology, leading to the triangulation of equal mixing of methods and increased reliability and validity of findings. This study addresses the research question, “Does NBE help support the prosocial skill development for children with ASD in preschool, and if so, in what ways?” Through qualitative analysis outdoors (Appendix H), I found children outdoors's flexible access to people, places, objects and self- establishing an Emotional Tenor of Contentment (Appendix I). Through quantitative analysis, I found that while the social climate of the class was stable indoors and outdoors, children engaged in more prosocial behaviors outdoors. Thus, the emotional tenor of contentment that children felt when outdoors set the stage for prosocial use and growth by creating opportunities for prosocial interactions. In summary, the Grounded Theory was ‘flexible access that children in NBE with ASD have to people, places, and objects, and self offers children an Emotional Tenor of Contentment, which in turn allows for opportunities for prosocial growth.’ An Autistic Researcher completed this study.