Preheat oven to 350 degrees. Spray a 9x13 pan with cooking spray and set aside.

In a large bowl, cream together butter and brown sugar. Add peanut butter, eggs, and vanilla. Continue to mix with electric mixer.

In small bowl, stir together flour, baking soda, and salt.

Gradually add flour mixture to large bowl and continue to mix until well combined.

Stir in oats, chocolate chips, peanut butter chips, and M&M's.

Spread batter into greased pan. Add additional M&M's to top, if desired.

Bake for 15 minutes or until edges are slightly brown. Let cool before slicing.