Preheat Oven: Preheat your oven to 350°F (175°C). Line baking sheets with parchment paper or silicone baking mats.

Cream Butter and Sugars: In a large mixing bowl, beat the softened butter, peanut butter, granulated sugar, and brown sugar together until smooth and creamy.

Add Wet Ingredients: Mix in the eggs and vanilla extract until fully incorporated.

Combine Dry Ingredients: In a separate bowl, whisk together the flour, baking soda, and salt. Gradually add the dry ingredients to the wet mixture, mixing until combined.

Fold in Mix-Ins: Gently fold in the oats, M&M candies, chocolate chips, and nuts (if using).

Form the Cookies: Scoop about 2 tablespoons of dough per cookie and roll into balls. Place them on the prepared baking sheets, spacing them about 2 inches apart.

Bake: Bake for 10-12 minutes, or until the edges are lightly golden. The centers may look slightly underbaked, which is fine as they will set while cooling.

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