In a medium bowl, mix all of the filling ingredients until the apples are evenly coated.
Transfer the apple mixture to a microwave-safe baking dish, spreading them out evenly.
In the same bowl used for apples, combine oats, brown sugar, flour, and cinnamon.
Add the cubed butter to the oat mixture. Use your fingers or a pastry cutter to blend the butter into the dry ingredients until the mixture resembles coarse crumbs.
Sprinkle the crumb topping evenly over the apples in the dish. Microwave on high for 7-15 minutes, or until the apples are tender. Cooking time will vary depending on the appliance, so check the doneness of the apples occasionally during cooking.