Monster Cookies are Franken-cookies that have everything but the kitchen sink in them! Feel free to add in raisins, Rice Krispies, nuts, or coconut, too!
Preheat oven to 350°F. In a mixer fitted with the paddle attachment, cream together 1 cup crunchy peanut butter, 1 stick butter, 1 ¼ cup brown sugar, and 1 cup granulated sugar until fluffy.
Add in 3 eggs and 1 teaspoon vanilla extract, and beat until mixed, scraping sides as necessary.
Add in ½ teaspoon salt, ½ cup flour, and 2 teaspoons baking soda and beat until well-mixed. Add in 3 cups old fashioned oats and mix on low until incorporated.
Remove the bowl from the mixer, and fold in ½ cup M&Ms and ½ cup chocolate chips by hand.
Form the dough into 2" balls and place on an ungreased baking sheet. Bake in preheated oven for 12-14 minutes, or until the cookies are just barely browned. Let cool for 5 minutes on the baking sheet, then transfer to a cooling rack to cool completely.