Place oven racks in the upper third of the oven and preheat to 350 degrees F. (177 degrees C.)
In a large bowl with an electric mixer, beat butter, brown sugar, and vanilla until light and fluffy, about 1 minute.
Add eggs one at a time and mix until thoroughly incorporated.
Add oats, flour, baking powder, cinnamon, nutmeg, and salt. Mix on low speed until blended.
Add semi-sweet chocolate chips and mix until incorporated.
Drop batter by heaping teaspoons 1 ½ inches apart onto greased or parchment-lined baking sheets. (we like a Silpat mat)
Bake for 10-13 minutes or until the edges of the cookies turn golden brown
Cookies will be soft but will firm up as they cool. Let cool for 2 minutes before transferring to wire cooling rack.
Notes
STORE baked cookies. Let the cookies cool completely on a wire rack before storing them. They can be kept at room temperature, in an airtight container, for about a week.STORE uncooked dough. To make this recipe ahead, follow the instructions and place the dough in the refrigerator for up to 3 days. No need to thaw the batter before baking. Simply add 1 minute to the baking time.FREEZING. cool your baked cookies completely and then transfer them to a freezer-safe, airtight container with parchment paper in between layers. Label and date and store them in the freezer until ready to eat. Nutritional information is approximate and was calculated using a recipe nutrition label generator and will vary based on cooking methods and brands of ingredients used.