Preheat the oven to 350 degrees.
Add butter, peanut butter, brown sugar, and sugar to a large mixing bowl.
Cream together for about 2 minutes, or until it starts to lighten (a stand mixer or hand held mixer is best).
Add in the vanilla and egg and mix until just combined.
Dump in the flour, salt, and baking soda. Stir them into the mixture until just combined.
Add in the oats, m&ms, and chocolate chips. Fold mixture together till they are mixed around evenly.
Measure out 1/4 cup of cookie dough and roll into a ball. Place 6-8 balls on a lined cookie sheet.
Slightly flatten cookie dough balls, to look more like a pancake. Smooth the edges as desired.
Press additional m&ms and chocolate chips onto the top if desired.
Bake cookies for 12-14 minutes until the edges start to turn golden and the tops crack a little.
Allow the cookies to cool on the cookie sheet for 3-4 minutes before moving them to a cooling rack to cool completely.