Preheat oven to 400°F. Line a baking sheet with parchment paper.
In a large mixing bowl, whisk together rolled oats, flour, baking powder, baking soda, salt, cinnamon, and nutmeg.
To the bowl of a stand mixer with the paddle attachment, add butter and brown sugar. Beat on low speed until smooth.
Add eggs, molasses, and vanilla. Mix until all ingredients are fully incorporated, stopping to scrape down the sides of the bowl as needed.
With the mixer still on low speed, slowly add the dry ingredients until fully incorporated.
Using a 2-tablespoon scoop, drop the dough onto the lined baking sheet. Gently press to flatten the cookies slightly.
Bake for 7-8 minutes. They may look slightly doughy, and that is okay.
Let the cookies rest on the baking sheet for a couple of minutes before transferring them to a wire rack to cool completely.