The study deals with the outdoor learning approach developed by Sreten Adžic (1856-1933), who is considered the founder of the outdoor learning movement in Serbia. He greatly influenced pedagogical practice as a primary-school teacher, professor, and teacher-training school manager. According to this approach, the term outdoor learning had two meanings: learning through exploring the local environment and staying outside the school building in green spaces during regular classes. This paper deals with the questions related to the theoretical and political foundations of that approach, its didactic characteristics, possible pedagogical, social, political and economic scope, and its position and role in the circulation of knowledge about the international context. The first part of the paper deals with the Pestalozzianism and socialism foundations of Adžic's practice at the beginning of his professional career. The second and third parts thematise outdoor learning as student-centred learning in an authentic context based on sense perception and students' self-activity. The local environment is interpreted as an educational object. This approach aimed to develop students' critical thinking and civic education. The fourth part presents the realisation of Adžic's project of outdoor classrooms as green spaces for learning and explains their pedagogical meaning. Key findings presented in the final part are those encouraging teachers to come outdoors contributed to rethinking the traditional teaching model and school education in giving a background for the new school movement, which was widely accepted in Yugoslavia between the two world wars.