The objective of this study was to gain an understanding of expert cognition in orienteering. The British orienteering squad was interviewed (N = 17) and grounded theory was used to develop a theory of expert cognition in orienteering. A task constraint identified as central to orienteering is the requirement to manage attention to three sources of information: the map, the environment, and travel. Optimal management is constrained by limited processing resources. However, consistent with the research literature, the results reveal considerable adaptations by experts to task constraints, characterized primarily by various cognitive skills including anticipation and simplification. By anticipating the environment from the map, and by simplifying the information required to navigate, expert orienteers can circumvent processing limitations. Implications of this theory for other domains involving navigation, and for the coaching process within the sport, are discussed.