The aim of this SCOTENS-funded project was to build teacher capacity for outdoor learning in mathematics through cross-border collaboration. The project sought to promote greater knowledge and understanding of how the outdoor environment can be used to support mathematics teaching in primary schools and to equip teachers with a variety of ideas for teaching mathematics outdoors. Given the decline in outdoor learning provision between the early years and later stages of primary education, it was decided to focus on upper primary mathematics. The aim of the project was to develop an online resource freely accessible to all teachers in order to support the planning and delivery of outdoor mathematics activities in upper primary classes. It is believed that the development of such a resource, with exemplar activities and case studies of effective practice in outdoor mathematics, will play an important role in improving children’s mathematical attainment as well as their ongoing health and wellbeing.