Preheat oven to 350 degrees, butter a large sheet pan (18 X 13 X 1 inch)
Using an electric mixer, mix sugars and eggs until well combined
Add in salt, vanilla, peanut butter, and butter until smooth
Add in baking soda and oats mixing well
Stir in M&M's and chocolate chips
Spread the very stiff batter into pan using your hands to pat evenly
Bake for 15-20 minutes making sure the center is set
Let cool before cutting into bars