Add oats, flour, baking powder, cinnamon, and nutmeg into a bowl.
In a separate bowl, beat butter with a hand mixer until creamy, add brown and white sugars, then beat until fluffy. Next add in the vanilla and eggs (1 at a time).
Pour the dry ingredients into the wet ingredients, mix
Take the dough and roll it into a ball. Then flatten into a cookie shape and put on a well-greased parchment-lined baking sheet. Repeat this process two more times with smaller balls to make the snowman shape.
Bake 12-15 minutes.
While cookies cool, combine the powdered sugar, milk, and warm water in a shallow bowl to make the icing.
Once the cookies have completely cooled, dip into the icing. Dry for 10 minutes or until icing has hardened.