Prepare Your Dry Ingredients: In a medium bowl, whisk together the flour, baking soda, baking powder, and salt. Add the rolled oats and mix until well combined.

Cream Butter and Sugars: In a large mixing bowl, beat the softened butter with brown sugar and granulated sugar until light and fluffy (about 2-3 minutes with an electric mixer).

Add Wet Ingredients: Beat in the eggs one at a time, followed by the vanilla extract. Scrape down the sides of the bowl to ensure even mixing.

Combine Wet and Dry Mixtures: Gradually add the dry ingredient mixture to the wet ingredients, mixing on low speed until just combined.

Add Mix-ins: If using raisins, chocolate chips, or nuts, fold them in gently at this stage.

Chill the Dough: Cover the bowl with plastic wrap and refrigerate for at least 30 minutes (up to 24 hours).

Bake to Perfection: Preheat oven to 350°F (175°C). Scoop 2-tablespoon portions of dough onto parchment-lined baking sheets, spacing them about 2 inches apart. Bake for 10-12 minutes, until edges are golden but centers still look slightly underdone.

Cool Properly: Let cookies cool on the baking sheet for 5 minutes before transferring to a wire rack to cool completely.