Preheat the oven to 350°F, line a 9x13 inch pan with parchment paper, and set aside.
Mix cookie dough and oats well.
Press cookie dough into bottom of prepared baking pan.
Bake for 15 minutes.
Remove from oven, and sprinkle ½ the chocolate chips and ½ the peanut butter chips over dough.
Pour sweetened condensed milk over everything. Sprinkle with remaining chocolate chips, peanut butter chips, and M&M’s.
Bake for 25 to 30 minutes or until the sweetened condensed milk has set.*
Remove from oven and let cool completely before slicing and serving.
Notes
*The condensed milk will begin to caramelize around the edges while remaining white in the center.Cookie bars can be kept at room temperature in a sealed container for about 4 days.Wrap individual portions in plastic wrap and freeze for up to a month.