Preheat oven to 325°F. Line a baking sheet with a silicone baking mat or parchment paper.

In a large bowl or stand mixer, cream together butter and sugars. Add egg and vanilla, mixing on low until combined. Add cinnamon, nutmeg, salt, baking powder, flour and oatmeal. Mix, increasing speed until ingredients are fulling incorporated and no streaks remain. Stir in chocolate chips by hand.

Divide dough with a large cookie scoop. Shape into even balls. Place on prepared baking sheet 2 to 3-inches apart. Flatten cookies to 3/4-inch using the palm of your hand.

Bake for 22-24 minutes or desired crispness. Allow cookies to rest on pan for 5-10 minutes prior to transferring to a wire rack to cool completely.

Store cookies in an airtight container. If desired, reheat cookies as desired for a softer cookie.