Monster Cookie Bars

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With or without ice cream and hot fudge, these Monster Cookie Bars are sure to be a hit! Peanut butter, M&Ms, oatmeal…they’re the trifecta of perfect cookie bar. These are better than pioneer woman and taste of home combined!

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stack of monster cookie bars

Have you ever had a monster cookie? It’s a peanut butter oatmeal cookie that’s filled with chocolate chips and M&Ms. I love them, because they’re a combination of two of my favorite cookie recipes. But as much as I like cookies, I think I like cookie bars better because there is no scooping. I just press the dough in the pan and bake it, easy peasy.

This recipe starts with my favorite peanut butter cookie recipe. I adapted it to add oats to make it MONSTER. And, of course, I added chocolate chips, regular M&Ms, and PEANUT BUTTER M&M’s. I swear, peanut butter M&M’s are my downfall. I can easily eat a 1 lb. bag all by myself!

Once you bake them they become a soft and gooey cookie bar that’s perfect for when you’re craving peanut butter and oatmeal cookies together.

stack of cookie bars on white plate with M&Ms and Ala mode

Ingredients in my Monster Bar Recipe

Butter: As always, I start with unsalted butter that’s been softened. Learn to soften butter quickly!

Peanut Butter: A must for monster cookies! You can use creamy or crunchy, but use a no-stir brand.

Sugar: Both granulated and brown sugar makes a soft and chewy bar.

Eggs: Be sure to buy large eggs.

Vanilla: For flavor

Salt: Needed when starting with unsalted butter!

Flour: I always use all-purpose flour, be sure to measure it correctly.

Quick Cooking Oats: I prefer baking with quick oats. To make these bars with old fashioned oats you just need to pulse the oats in a food processor to break them down – learn to make your own quick oats!

Mix-Ins: Chocolate Chips and M&Ms

  1. Preheat oven to 350°F. Line a 9×13” pan with foil and spray with nonstick cooking spray.
  2. Beat butter and peanut butter with a hand or a stand mixer until smooth. Mix in both sugars until creamy. Add eggs, vanilla, baking soda, and salt and mix until smooth, then slowly mix in the flour and oats. Stir in the chocolate chips and M&Ms.
  3. Press cookie dough into the prepared pan. If desired, sprinkle more M&Ms on top for decoration. Bake for 22-25 minutes or just until the edges are golden brown.
stack of cookie bars

Variations and Expert Tips

  • Make Christmas Monster Cookie Bars with holiday M&Ms
  • Reese’s Pieces Monster Cookie Bars would be fantastic – just swap the M&Ms for Reese’s Pieces!
  • Do not over bake these – they’re best a little under baked and gooey
  • How to serve Monster Bars: I love serving these plain, just as a bar cookie, or topping with ice cream!
How long to bake monster cookie bars?

Bake these 22-25 minutes or until they just lose their glossy sheen.

How to store cookie bars? Can you freeze monster cookie bars?

Store these in an airtight container. Freeze for up to 3 months.

Can you make monster cookie bars into cookies?

It’s not an exact swap so I suggest making gluten free monster cookies instead.

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Monster Cookie Bars – this easy bar cookie recipe is full of peanut butter, oats, and tons of M&Ms! EVERYONE loves these, especially with ice cream!
No ratings yet
Prep Time 15 minutes
Cook Time 30 minutes
Total Time 45 minutes
Yield 24 bars
Serving Size 1 bar

Ingredients

  • ½ cup (113 g) unsalted butter softened
  • 1 cup (268 g) peanut butter
  • ¾ cup (150g) packed brown sugar
  • ½ cup (100g) granulated sugar
  • 2 large eggs
  • 1 teaspoon vanilla extract
  • ½ teaspoon baking soda
  • ½ teaspoon salt
  • ¾ cup (93g) all-purpose flour
  • 3 cups (256g) quick cooking oats
  • 1 cup (170g) chocolate chips
  • 2 cups M&Ms any kind, I used regular and peanut butter

Instructions

  • Preheat oven to 350°F. Line a 9×13” pan with foil and spray with nonstick cooking spray.
  • Beat butter and peanut butter with a hand or a stand mixer until smooth. Mix in both sugars until creamy. Add eggs, vanilla, baking soda, and salt and mix until smooth, then slowly mix in the flour and oats. Stir in the chocolate chips and M&Ms.
  • Press cookie dough into the prepared pan. If desired, sprinkle more M&Ms on top for decoration. Bake for 22-25 minutes or just until the edges are golden brown. Cool before cutting into bars.
  • These are great served as bars or as an ice cream sundae! Store in an airtight container for up to 3 days or freeze for up to one month.

Recipe Video

Nutrition Information

Serving: 1bar | Calories: 322kcal | Carbohydrates: 40g | Protein: 6g | Fat: 16g | Saturated Fat: 7g | Polyunsaturated Fat: 2g | Monounsaturated Fat: 4g | Trans Fat: 1g | Cholesterol: 28mg | Sodium: 146mg | Potassium: 126mg | Fiber: 2g | Sugar: 28g | Vitamin A: 194IU | Vitamin C: 1mg | Calcium: 48mg | Iron: 1mg

Nutritional information not guaranteed to be accurate

Course Dessert
Cuisine American
Keyword cookie bar

Click here to see more PEANUT BUTTER recipes! 

When I used to write stories:

When I was in the throes of toddlerhood, I would never have guessed the challenges of parenting an older kid. Jordan is now 11 (and a half!) and she’s in that weird in-between stage between needy kid and more self-sufficient teenager. She’s also the first (and only) child, so I’ve never crossed any of these parenting situations before. It’s all new to me, which makes me a tad more overprotective and worried than, say, someone whose done it all a few times.

Pretty much daily these days I’m faced with scary decisions: can she stay in the car while I run into Starbucks? Can she stay home alone? Can she walk the dog alone? Is it okay to let her run into the grocery store by herself to buy gum? Every time a situation pops up my stomach clenches in fear and indecision: what do I do?

Last week Mel was out of town so we went to my parent’s house for a few days. It’s a 2-hour drive and neither of us can make it without stopping. We had the dog with us, and it was 105°. For days before we left, the question played through my mind of exactly how to go to the bathroom in this situation. Do I leave them both in the running car (with A/C) while I go into the gas station? Or do I make them get out and stand outside while I do my thing? Should I stop at Taco Bell or the gas station? Mind you, both scenarios have Jordan going into a restroom in a very public place alone.

I seriously wrestled with the decision of what to do for days. I woke up at 4am the day we left having anxiety and almost panic-attacks. You guys, this parenting thing is HARD!

Ice cream + cookie bars can really fix any parenting problem, don’t you think?

(Oh, and we made there and back, stopping both times, and Jordan didn’t get kidnapped. #ThankGoodness)

Last Updated on February 19, 2022

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18 CommentsLeave a comment or review

  1. Looks yummy! I think it shows you’re a good mom that you’re thinking about these things!