An increasing number of Danish teachers have started introducing school-based outdoor learning as a weekly or biweekly "outdoor school" day for school children--often called "udeskole" in Danish. Although at least 14% of Danish schools practise this form of outdoor teaching with some classes, it is not mentioned in the national curriculum and little is presently known about the nature of "udeskole." Drawing on a conceptual framework about different curriculum domains, we explore outdoor learning theory and practice in Danish schools. We describe and analyse the advocated pedagogy and didactics of the Danish "udeskole" movement as well as current practice through a review of the literature and a nationwide survey of 107 responding teachers. We also reveal discrepancies between the advocated and practised outdoor learning curriculum. Finally, we present recommendations on how to bridge these gaps and develop the practice further. (Contains 1 note, 2 figures, and 4 tables.)