In a mixing bowl, thoroughly mix together the oats, sugar, flour, baking powder, cinnamon, salt, ginger and nutmeg. Cut the butter into pieces and work it into the dry ingredients with your fingers or a pastry cutter until it resembles coarse crumbs. Transfer to a re-sealable plastic bag and freeze until ready to use.
To use: Preheat an oven to 375 degrees F. Add enough fresh or frozen fruit to an oven-safe dish to fill almost to the top. Sprinkle the fruit with the oat crumb mixture evenly and then bake until the fruit is soft and it starts to bubble around the sides, 40 to 45 minutes, depending on the fruit variety and size of the cooking vessel.