Oil the grill rack. Transfer the crust to the grill. Close the lid and cook until puffed and lightly browned, 1 to 2 minutes. Using tongs, turn the crust over. Spread the crust with the hummus and top with the squash and the feta. Close the lid and cook until the cheese is melted and the crust is lightly browned on the bottom, 2 to 3 minutes more.