Monster Cookie Bars that are soft, peanut butter flavored, oats, chocolate chips, peanut butter chips, and M&Ms. This dessert is a crowd pleaser!

monster cookie dough bars on a blue surface with M&Ms

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MONSTER COOKIE BARS

These Monster Cookie Bars are everything you love about monster cookies – chewy oats, plenty of peanut butter, chocolate chips, peanut butter chips and colorful M&Ms – pressed into one 9×13 pan. No scooping, no rolling, no batches. Just mix one bowl, bake 20 minutes and cut into thick, soft bars that feed a crowd.

WHAT MAKES THESE DIFFERENT

These bars are different in that they use an extra egg yolk keeps them chewy for days, a generous scoop of peanut butter and peanut butter chips, and a little extra salt makes all that sweetness taste balanced instead of cloying.

  • Faster than cookies. One pan instead of four trays of cookies.
  • Thick and chewy, not cakey. One whole egg plus one yolk gives that soft, bendy center.
  • Triple the mix-ins. Chocolate chips, peanut butter chips and M&Ms in every bite.
  • Real peanut butter flavor. 3/4 cup of peanut butter, more than many recipes use.
  • Great for a crowd. Bake sales, potlucks, lunchboxes and game day.baked monster cookie dough bars

What Are Monster Cookies?

Monster cookies are a Midwest classic: a peanut butter oatmeal cookie loaded with chocolate chips and M&Ms. Monster cookie bars take that same dough and bake it in a pan, so you get the flavor with a fraction of the work.

Ingredients You’ll Need

  • All-purpose flour: Not too much, so the bars stay soft instead of dry.
  • Old-fashioned oats: They give more chew and texture than quick oats.
  • Butter: Unsalted, so you control the salt.
  • Brown and white sugar: Brown sugar for chewiness and caramel flavor, white sugar for crisp golden edges.
  • Creamy peanut butter: Use a regular brand like Jif or Skippy. Natural peanut butter separates and makes the bars greasy and crumbly.
  • Egg plus an egg yolk: The extra yolk is the secret to chewy bars.
  • Salt and baking soda: Salt balances the sweetness; baking soda gives a little lift.
  • Mix-ins: Peanut butter chips, semi-sweet chocolate chips and M&Ms.

monster cookie dough bars on a blue surface with M&Ms

See the recipe card below for exact amounts.

  1. Prep the pan. Grease the pan or line a 9×13 pan with parchment, leaving an overhang so you can lift the bars out.
  2. Cream the butter, sugars and peanut butter until light and fluffy.
  3. Add the egg, yolk and vanilla and mix until smooth.
  4. Add the dry ingredients – flour, baking soda and salt – then stir in the oats.
  5. Fold in the mix-ins, saving a handful of M&Ms and chips for the top.cookie dough in a pan
  6. Press into the pan in an even layer and press the reserved candies on top.
  7. Bake at 350°F for about 20 minutes, until the edges are golden and the center looks just set.
  8. Cool completely before slicing.
  • Pull them early. The center should look barely set. Bars keep baking in the hot pan, and overbaking is the number one cause of dry bars.
  • Press candies on top right out of the oven. Pressing a few extra M&Ms and chips into the warm bars makes them look bakery-perfect.
  • Let them cool fully. Warm bars crumble. Cool at least 1 hour for clean squares.
  • Use a sharp knife and wipe it between cuts for neat edges.
  • Don’t use natural peanut butter. It changes the texture.
  • Room temperature: Airtight container for up to 4 days.
  • Freezer: Wrap bars individually in plastic wrap, place in a freezer bag and freeze up to 3 months. Thaw on the counter for about 30 minutes.

monster cookie dough bars on a blue surface with M&Ms

monster cookie dough bars on a blue surface with M&Ms

Monster Cookie Bars

Christy Denney
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Thick, chewy monster cookie bars loaded with peanut butter, oats, chocolate chips, peanut butter chips and M&Ms, baked in one 9x13 pan.
Print Pin Rate
Prep Time: 15 minutes
Cook Time: 25 minutes
Total Time: 40 minutes
Servings: 24 bars

Ingredients
  

Instructions
 

  • Preheat the oven to 350°F. Grease a 9x13-inch pan or line with parchment paper, leaving an overhang on two sides.
  • Beat the butter, brown sugar, granulated sugar and peanut butter on medium speed until light and fluffy, about 2 minutes.
  • Beat in the egg, egg yolk and vanilla until smooth.
  • Add the flour, baking soda and salt and mix on low just until combined. Stir in the oats.
  • Fold in the peanut butter chips, chocolate chips and M&Ms, saving a small handful of each for the top.
  • Press the dough evenly into the pan. Scatter the reserved mix-ins on top and press lightly.
  • Bake 20–22 minutes, until the edges are golden and the center looks just set. Do not overbake.
  • Press a few extra M&Ms into the warm top if desired. Cool completely in the pan, at least 1 hour, then lift out and cut into bars.

Notes

Pull the bars when the center still looks slightly soft; they finish setting as they cool.
Use regular creamy peanut butter. Natural peanut butter makes the bars greasy and crumbly.
Store airtight at room temperature up to 4 days, or freeze individually wrapped up to 3 months.
Cuisine: American
Course: All Desserts, All Recipes, Dessert
Author: Christy Denney

monster cookie dough bars on a blue surface with M&Ms

monster cookie dough bars on a blue surface with M&Ms