Preheat oven to 350 degrees F.
Line two cookie sheets with parchment paper. Set aside.
Cream peanut butter, butter, and sugars together in a stand mixer. Or use a bowl and hand mixer.
Add the eggs and vanilla to the mixing bowl and mix again.
Next, add the oats, flour, baking soda, baking powder and salt, combine thoroughly.
Add the chocolate chips and ¾ cup of the M&M's to the dough. Stir with a spoon this time so the chocolate stays in whole pieces. Be sure to reserve ¼ cup of the M&M's to press into the tops of the cookies once they are baked.
Form heaping tablespoons of dough into balls, place on parchment lined baking sheet.
Now flatten them a little bit.
Bake in the preheated 350 degrees F oven for 12 - 15 minutes.
Remove from oven, and press the rest of the M&M's into the tops of the cookies.
Use a spatula to slide the baked cookies onto a wire rack and allow them to cool completely.
Serve with a big old Monster cookie loving smile!