Preheat the oven to 350 degrees F. Line the bottom and sides of a 9x9 inch baking pan with parchment paper and set aside.

Whisk together the flour, oats, baking soda, and salt in a medium bowl and set aside.

In a large bowl, beat the butter, peanut butter, and sugars with a hand or stand mixer until light and fluffy.

Scape the sides of the bowl and beat in the eggs and vanilla until well combined.

Scrape the bowl again and add the flour and oat mixture. Mix until just combined, do not overmix.

Set aside ¼ cup of M&Ms and two tablespoons each of the chocolate and peanut butter chips. Fold the remaining M&Ms, chocolate, and peanut butter chips into the cookie dough.

Turn the cookie dough into the prepared pan and gently press into an even layer smoothing the top with a rubber spatula or the back of a spoon.

Scatter the M&Ms, chocolate, and peanut butter chips that you set aside over the top of the cookie dough and gently press down.

Bake for 22-28 minutes or until the edges have set and a toothpick inserted into the center comes out clean.

Press the candy eyeballs into the cookie bars while they are warm, then allow them to cool completely in the pan before removing and cutting them into squares.