Preheat oven to 350°F (175°C) and line baking sheets with parchment paper.

Pulse oats in a food processor 8-10 times until they resemble a coarse flour. Do not grind into fine powder.

In a medium bowl, whisk together pulsed oats, flour, baking powder, baking soda, salt, cinnamon, and nutmeg.

In a large bowl or stand mixer, cream softened butter, brown sugar, and granulated sugar until light and fluffy (approx. 2-3 mins).

Add eggs one at a time, mixing well after each. Stir in vanilla extract.

Gradually mix in the dry ingredients on low speed until just combined. Do not overmix.

Scoop dough (approx 2 tbsp) onto baking sheets, spacing them 2 inches apart.

Bake for 10-12 minutes until edges are golden. Centers may look slightly soft. Cool on pan for 5 minutes, then transfer to wire rack to cool completely.

Whisk powdered sugar, milk, and vanilla until smooth and thick. Dip the tops of cooled cookies into icing or drizzle generously.

Allow icing to set and harden before serving or storing.