Monster Cookie Bars are a denser, bar-shaped take on the classic chewy peanut butter, oat, and M&M cookie. Packed with peanut butter, oats, chocolate chips and colorful candies, these bars deliver the flavors of a monster cookie in every rich, chewy bite.
I love cookie bars and all the comforting ingredients that go into monster cookies: peanut butter, oats, chocolate chips and M&M’s. Turning that combination into a bar makes the texture denser and even more satisfying—perfect for packing in lunches, sharing at parties, or enjoying as an indulgent snack.
This version has been tested both with regular and gluten-free ingredients. Swap in a gluten-free flour blend and certified gluten-free oats if you need a gluten-free option—the bars keep the same texture and flavor. I also tend to load these with extra chocolate chips, M&Ms and peanut butter, resulting in a generously packed bar that’s deeply chocolatey and peanut-butter forward.
A quick note on peanut butter: I use an all-natural smooth peanut butter for the best flavor, but regular smooth peanut butter works fine as well. Avoid crunchy peanut butter for this recipe because the smooth texture and moisture content help create the soft, cohesive crumb these bars need.
These bars come together quickly and bake into a slightly underdone center for a gooey, soft result. They’re ideal when you want something that tastes like a cookie but is easier to slice, serve, and transport. Below you’ll find the full recipe, ingredient list and instructions so you can make these at home.
Monster Cookie Bars
Ingredients
- ⅓ Cup Butter, Softened (80g)
- ¾ Cup Brown Sugar (130g)
- ½ Cup Sugar (100g)
- ¾ Cup Smooth Peanut Butter (188g)
- 2 Large Eggs
- 1 Tbsp. Vanilla Extract
- 1 and ½ Cups Old Fashioned Rolled Oats (135g)
- 1 Cup All Purpose Flour (or Gluten Free Flour Blend) (120g)
- 1 teaspoon Baking Soda
- 1 Cup M&Ms (200g)
- 1 Cup Chocolate Chips (180g)
Instructions
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Preheat the oven to 180°C (350°F). Line a 9″x9″ baking pan with parchment paper or grease it well and set aside.
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In a large bowl, beat the softened butter, brown sugar, sugar and smooth peanut butter together with an electric mixer until light and fluffy.
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Add the eggs and vanilla extract and beat until fully combined and smooth.
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Stir in the oats, flour and baking soda until the mixture is evenly combined.
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Fold in the M&Ms and chocolate chips, then press the dough evenly into the prepared pan.
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Bake for 20–25 minutes, until the edges are lightly golden and a skewer inserted in the center comes out with a few moist crumbs. For soft, gooey bars, avoid overbaking.
Nutrition
