This post may contain affiliate links. Please read our disclosure policy.
These soft and chewy peanut butter oatmeal Monster Cookie Bars are loaded with chocolate chips and colorful M&M’s. This recipe is perfect for a quick and easy batch of sweet treats for any party or celebration!
Need more dessert recipes? You might like our churro cinnamon bars, brown butter chocolate chip cookies, and our Mexican Wedding Cookies.
Why I Love These Monster Cookie Bars
- Fun: How can these be anything but fun with the colorful chocolate candies sprinkled throughout? Plus with a name like monster, these cookie bars would be a show stopper with little candy eyes for a Halloween themed party.
- Family Friendly: The fun colors and name make these a perfect treat for our younger people (just like these Oreo Bars!).
- Textures: A combination of all purpose flour and rolled oats gives a nice bite to the bars, just like our Cowboy Cookies.
Ingredients
Peanut Butter: This recipe has been tested with organic natural peanut butter and Jif creamy peanut butter. The natural version comes out more crumbly in texture. The version with Jif is more chewy, but also sweeter since this peanut butter has sugar.
How to Make Monster Cookie Bars
Mix Wet Ingredients: Cream together the room temperature butter and peanut butter to create a smooth mixture. Add in the eggs, vanilla and maple syrup. Mix together until smooth and creamy.
Mix Dry and Combine: In a small bowl combine the dry ingredients of all purpose flour, rolled oats, baking soda and salt. Add the dry ingredients into the wet ingredients, mixing to combine, the dough will be thick. Fold in the chocolate chips and chocolate candies.
Prepare to Bake: Scoop the dough into an 8×8 baking pan that has been lined with parchment paper. Using parchment paper allows you to easily remove the bars from the pan after baking. Spread the dough into an even layer in the baking pan and top with additional chocolate candies and chocolate chips to ensure the top of the bars are colorful and look beautiful after baking.
Bake the monster cookie bars in the oven at 350 degrees F for 30-35 minutes until baked through, top will be golden. Allow the bars to cool completely before slicing. If they’re too warm they will crumble.
Variations
- Colors: Switch out the M&M colors for a holiday theme or a particular sports team.
- Additional Candy: Add miniature Reese’s or peanut butter chips, for even more peanut butter flavors.
- Candy Eyes: Press some candy eyes into the tops of the cookie bars for a fun Halloween themed treat.
Storage Information
- Make Ahead: Prepare the dough, cover and chill in the refrigerator for up to 48 hours. Let the dough come to room temperature before pressing into the pan and baking.
- Storage: Store in a sealed container at room temperature for up to 3 days.
- Freezing: Place baked monster cookie bars in a freezer safe container or bag and store for up to 3 months.
Monster Cookie Bar Recipe
Ingredients
- ½ cup unsalted butter room temperature
- ¾ cup peanut butter use creamy Jif or Skippy style
- ½ cup light brown sugar
- ¼ cup white sugar
- 2 tablespoons maple syrup
- 1 teaspoon vanilla extract
- 1 large egg
- 1 large egg yolk
- 1 cup all purpose flour
- ½ cup rolled oats
- ¼ teaspoon salt
- ½ teaspoon baking soda
- ½ cup chocolate chips
- ½ cup chocolate candies
Instructions
- Preheat oven to 350 degrees F.
- Line an 8×8 baking pan with parchment paper, leave some overhang on the side to help pull out the bars after baking.
- In a large mixing bowl add the butter and peanut butter. Mix using a hand mixer until smooth and creamy.
- Add in the sugars and mix until well combined and fluffy.
- Add in the egg, egg yolk, vanilla, and maple syrup. Mix to just to combine.
- In a medium size mixing bowl combine the flour, oats, salt and baking soda. Stir this together with a fork.
- Slowly add the dry ingredients to the wet, mix with the hand mixer until just combined.
- Pour in the chocolate chips and chocolate candies. Fold in with a spoon.
- Spoon the dough into the prepared baking pan. Spread out with the back of the spoon until level.
- Top with additional chocolate chips and candies gently pressing into the dough.
- Bake at 350 degrees for 30-35 minutes until cooked through. Sides and top will be golden.
- Let bars cool in the pan for at least 30 minutes, then remove from the pan.
- Continue to let the bars cool completely before cutting.
Equipment
Notes
- Make Ahead: Prepare the dough, cover and chill in the refrigerator for up to 48 hours. Let the dough come to room temperature before pressing into the pan and baking.
- Storage: Store in a sealed container at room temperature for up to 3 days.
- Freezing: Place baked monster cookie bars in a freezer safe container or bag and store for up to 3 months.
- Peanut Butter: This recipe has been tested with organic natural peanut butter and Jif creamy peanut butter. The natural version comes out more crumbly in texture. The version with Jif is more chewy, but also sweeter since this peanut butter has sugar.
- Chocolate Candies: I have found the Unreal brand chocolate candies tend to have a burnt taste if pressed into the top of these bars then baked. If you choose to use that brand I would skip that step and just have them mixed into the dough.
Nutrition
Nutrition information is automatically calculated, so should only be used as an approximation.
Photography and styling by Jess Gaertner.
