Physical activity in Canada mirrors the gender gap observed globally, with boys more likely than girls to meet recommended guidelines. While a growing body of research has examined the relationships between environmental factors and children’s physical activity levels, much less is known about how environments play a role in gendering physical activity. In this paper, using a material feminist approach to environmental affordances, we explore girls’ perspectives on the features of their everyday environments that support or inhibit their uptake of physical activities in Southwestern Ontario, Canada. As part of the larger multi-method Spatial Temporal Environment and Activity Monitoring (STEAM) project, we held six focus groups with girls ages 10–12 years from rural, suburban, and urban schools. Through inductive thematic analysis, we identified two themes: (1) Outdoor matter matters for physical activity, and (2) Social levers and liabilities shape physical activity affordances. Our results indicate that some girls may be better afforded physical activity opportunities by providing proximate outdoor play in spaces with natural elements and diverse infrastructure, coupled with efforts to alleviate social liabilities (e.g., care responsibilities) and leverage social supports (e.g., peers). Based on our findings, we put forward naturalised schoolyards as a potentially gender-sensitive physical activity intervention. This study contributes to identifying the gendered ways in which environments may differentially ‘afford’ children opportunities for physical activity, thereby opening the way for developing more gender-equitable interventions.