Whisk together the oats, flour, baking soda, and salt

In a separate bowl, cream together the butter, peanut butter, sugar and brown sugar until smooth. Add the eggs and vanilla extract and beat to combine

Add the dry ingredients to the wet and mix to combine

Fold in ¾ cup of chocolate chips and ½ cup of M&M’s

Spray the bottom of a 9 by 13 baking dish, then line it with parchment paper to overhang the sides (this will make it easier to get the bars out)

Use a rubber spatula to press the monster cookie batter into the lined baking dish

Top with additional M&M's

Bake at 350 degrees for 23 - 27 minutes, until very lightly browned on the edges. Remove and allow to cool completely (or at least one hour). The bars will continue to cook in the pan so be careful not to over bake them. 

Once the bars have cooled, remove them from the baking dish and cut into 12 large pieces, or 18 smaller bars

Store leftover bars in an airtight container