Preheat the oven to 350°F. Grease a 9x13 inch baking dish with a cooking spray.
Put the rolled oats in a small bowl and cover with boiling water. Set aside.
In a large mixing bowl, cream together softened butter with granulated sugar and packed brown sugar using an electric mixer. Then, add eggs and vanilla extract and beat until well combined. Add cooled rolled oats. Beat until combined. Then, add all-purpose flour, baking soda, salt, ground cinnamon, and ground nutmeg. Beat until combined.
Pour the batter into the prepared baking dish. Bake in the preheated oven for 30 minutes or until oatmeal cake is set. You can also check the readiness of the oatmeal cake using a toothpick inserted in the center, if it comes out clean - the cake is ready.
While the oatmeal cake is baking, prepare the topping. In a large bowl, mix together melted butter, flaked coconut, almonds, packed brown sugar, and evaporated milk.
Remove the oatmeal cake from the oven and spread evenly the coconut topping over the top.
Switch the oven mode to broil. Broil the oatmeal cake until the top is brown and the coconut is toasted. Let it cool in the pan. Then, slice and enjoy!