Pour water over oatmeal; let stand 20 minutes.

Beat butter until it's creamy, gradually beat in sugars.

Add vanilla and eggs. Blend well.

Stir in flour, baking soda, salt, cinnamon, and nutmeg until all ingredients are blended and moistened.

Pour into greased and floured 9 inch square pan.

Bake at 350 degrees for 50 minutes.

Let cool.

Combine remaining ingredients until well blended and spread over cooled cake.