Preheat your oven to 350°F.
In the bowl of a stand mixer, combine the melted butter, granulated sugar, brown sugar, and vanilla. Mix on low until everything is well combined.
Add the eggs and mix on low until fully incorporated.
With the mixer on low, slowly add in the flour, baking soda, instant vanilla pudding, and salt. Mix until everything is evenly combined.
Remove the bowl from the stand mixer and gently fold in the chopped Oreos and M&Ms using a rubber spatula.
Line a baking sheet with parchment paper. Using a medium-sized cookie scoop (about 2 tablespoons of dough per cookie), place 6-8 cookies on the prepared baking sheet, ensuring they are at least 1 inch apart.
Bake for 9 minutes or until the edges just start to turn golden brown. Remove them when they are just barely baked. For a decorative touch, press 2-3 M&Ms and Oreo pieces into the cookies while they are still hot.
Allow the cookies to sit on the baking sheet for 3-4 minutes before transferring them to a cooling rack to cool completely. Avoid overbaking to keep them soft and chewy.
These cookies will stay fresh for up to 1 week and can be frozen in an airtight container for up to 3 months. Enjoy the delightful flavors!