In their review of evidence-based research entitled "A Review of Research on Outdoor Learning," Rickinson "et al." (2004) identify five key constraints that limit the amount of outdoor learning. This paper explores whether green school grounds might be a location where these constraints could be minimised. Specifically, it reports on a study that sought to investigate the use of green school grounds as sites for outdoor learning, to identify barriers that impede such use, and to examine how these barriers differ from those cited in Rickinson "et al."'s review. A mixed method approach was used: (1) 149 questionnaires were completed by administrators, teachers, and parents associated with 45 school ground greening initiatives in a Canadian school board; (2) 21 follow-up interviews were completed at five of the schools. Study participants reported that green school grounds are used regularly for teaching some subjects, notably science and physical education, but considerably less for teaching language arts, mathematics, and geography. They also identified a series of barriers that limit the amount of outdoor learning and these are compared to those identified by Rickinson "et al." (2004). This paper concludes with a discussion of how the opportunities for teaching and learning on green school grounds can be more fully maximised. (Contains 4 tables and 6 notes.)