Preheat and prep: Heat the oven to 350°F (175°C). Line two baking sheets with parchment paper for easy cleanup.

Cream the butter and sugars: In a large bowl, beat the butter, brown sugar, and granulated sugar until light and fluffy, about 2–3 minutes. This step gives you that soft, chewy texture.

Add eggs and vanilla: Beat in the eggs one at a time, then mix in the vanilla. Scrape the bowl so everything blends well.

Whisk the dry ingredients: In a separate bowl, whisk the flour, baking soda, baking powder, cinnamon, salt, and nutmeg (if using).

Combine: Add the dry mixture to the wet ingredients and mix on low until just combined. Do not overmix.

Fold in oats and add-ins: Stir in the rolled oats and your chosen add-ins until evenly distributed.

Chill (optional but helpful): For thicker cookies, chill the dough for 20–30 minutes. If you’re in a hurry, you can skip it.

Scoop and space: Use a tablespoon or cookie scoop to drop rounded balls of dough onto the prepared sheets, spacing about 2 inches apart.

Bake: Bake 9–11 minutes, until the edges are set and lightly golden and the centers still look a touch soft. They’ll finish setting as they cool.

Cool: Let cookies cool on the sheet for 5 minutes, then move to a rack to cool completely. Enjoy warm or at room temperature.