In eye-tracked augmented and virtual reality (AR/VR), instantaneous and accurate hands-free selection of virtual elements is still a significant challenge. Though other methods that involve gaze-coupled head movements or hovering can improve selection times in comparison to methods like gaze-dwell, they are either not instantaneous or have difficulty ensuring that the user’s selection is deliberate. In this paper, we present EyeShadows, an eye gaze-based selection system that takes advantage of peripheral copies (shadows) of items that allow for quick selection and manipulation of an object or corresponding menus. This method is compatible with a variety of different selection tasks and controllable items, avoids the Midas touch problem, does not clutter the virtual environment, and is context sensitive. We have implemented and refined this selection tool for VR and AR, including testing with optical and video see-through (OST/VST) displays. Moreover, we demonstrate that this method can be used for a wide range of AR and VR applications, including manipulation of sliders or analog elements. We test its performance in VR against three other selection techniques, including dwell (baseline), an inertial reticle, and head-coupled selection. Results showed that selection with EyeShadows was significantly faster than dwell (baseline), outperforming in the select and search and select tasks by 29.8% and 15.7%, respectively, though error rates varied between tasks.