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CPA: Certified Pastry Aficionado

Monster Cookie Bars

bars and brownies· Cookies
October 4, 2018

Jump to Recipe Print Recipe

Monster Cookie Bars – All the flavors of the classic monster cookie – peanut butter, oatmeal, chocolate chips, M&M’s,- but now in an easy-to-make bar!

Monster Cookie Bar squares with m&ms and chocolate chips

Man, this year sure has flown by, hasn’t it?! I cannot believe we are already heading into October. Before you know it, we’ll be buying a Christmas tree and decking the halls!

As you are well-aware, I like to start each month with a new cookie recipe. Last month, I rang in the fall season with these Pumpkin Oatmeal Cream Pies. But for this month’s cookie, I am taking a break from fall and sharing a new take on a classic cookie – monster cookies, to be specific.

For today’s recipe, I am turning monster cookies into an easy-to-make bar. No need to form the dough into balls – simply dump the dough into a 9×13 baking pan and bake. Then, just slice and serve! You cannot get more simple than that!

Without further ado, here are my Monster Cookie Bars!

Pan of Monster Cookie dough before being cut into bars Pan of cookies with chocolate chips and m&ms Stack of Monster Cookie Bars

If you haven’t heard of or had a monster cookie before, let me explain exactly what it is. A monster cookie gets its name from the amount of ingredients that are in it. It’s an oatmeal cookie loaded with chocolate chips, peanut butter, and M&M’s – basically all my favorite things in one chewy dessert!

Instead of making cookies (which I’ave already done here), I wanted to make these cookies in bar-form. I love a great cookie bar – mostly because I get all the flavor and texture of a cookie but without all the effort. Rolling cookie dough into perfect balls before baking can get exhausting so this is a great alternative. Plus, you don’t have to chill the dough when making bars, which is another bonus!

Top view of a stack of Monster Cookie Bars Stack of Monster Cookie Bars surrounded by m&ms Monster Cookie Bars cut into squares

This recipe is pretty straight-forward. But, as always, I have a few tips to help you along the way:

  1. The most important tip I can give you when making bars or brownies is to make sure you adjust your oven based on the type of baking pan you’re using. If you are using a dark-colored metal baking pan, always reduce the oven temperature by 25 degrees. This ensures that the center cooks just as evenly as the edges.
  2. Do not over-bake these bars! As soon as you see the edges getting golden brown, remove them from the oven. You don’t want these babies to get dry.
  3. Make sure you use quick-cooking oats, not instant oats. Instant oats will make these bars too mushy.

And there you have it – this month’s cookie recipe! What other kinds of cookies are you baking this month? Let me know in the comments below!

Monster Cookie Bars

Print Recipe

Monster Cookie Bars

All the flavors of the classic monster cookie - peanut butter, oatmeal, chocolate chips, M&M's,- but now in an easy-to-make bar!
Prep Time10 minutes mins
Cook Time15 minutes mins
Total Time35 minutes mins
Servings: 18 bars

Ingredients

  • 1 stick butter unsalted, softened
  • 1 cup light brown sugar
  • 1/2 cup creamy peanut butter
  • 2 large eggs
  • 1 teaspoon pure vanilla extract
  • 1 3/4 cups all-purpose flour
  • 1 teaspoon baking soda
  • 1 teaspoon salt
  • 1 3/4 cups quick-cooking oats
  • 3/4 cup semi-sweet chocolate chips
  • 1 cup mini M&M's

Instructions

  • Preheat oven to 350 degrees. Line 9x13 pan with parchment paper. Set aside.
  • Beat butter and sugar together in a large bowl of a stand mixer until creamy. Add peanut butter and vanilla and combine. Add eggs one at a time until combined.
  • In a separate medium bowl, add flour, baking soda, salt, and oats. Whisk until combined. Add dry ingredients to mixer and mix on low just until combined. Add chocolate chips and 1/4 cup of M&M's. Mix just until evenly distributed in dough.
  • Scoop dough into prepared baking pan. Using your hands, press dough firmly in pan to spread it evenly. Sprinkle remaining 1/2 cup of M&M's over dough and press them into dough.
  • Bake for 14-16 minutes, or until edges are browned and center is cooked. Remove from oven and let them cool for at least 10 minutes before cutting.

Notes

Recipe adapted from Chocolate with Grace

Pin for later:

Monster Cookie Bars photo collage

More recipes you’ll love:

Monster Cookies

Monster Cookies - Super chewy oatmeal cookies with peanut butter, M&M candies, and chocolate chips. And naturally they're gluten free!

Pumpkin Oatmeal Cream Pies

Reese’s Pieces Peanut Butter Cookies

Reese's Pieces Peanut Butter Cookies - Soft and dense peanut butter cookies, with chocolate chips and Reese's pieces candy. A chewy cookie that kids and adults will both love!

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24 Comments

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Comments

  1. Abby says

    October 1, 2020 at 5:52 am

    I’d like to divide this into two 8×8 pans. How would the bake time change if I did that?

    Reply
    • Sharon says

      October 3, 2020 at 7:32 am

      I haven’t made these in smaller pans but first try reducing by 10-15 minutes and then just monitor so they don’t over bake

      Reply
  2. Emily Leary says

    October 10, 2018 at 4:13 am

    Oh man! These look so good. I need a big slice with some hot chocolate right now. The kids would go crazy for these too.

    Reply
  3. Holly says

    October 7, 2018 at 11:25 pm

    I love these monster bars! They are perfect for entertaining and sharing during the holidays!

    Reply
  4. charity says

    October 7, 2018 at 10:25 pm

    I love the idea of an oatmeal cookie bar….adding peanut butter and M&Ms is a decadent idea, of which I wholly approve. Do you think i could get by with just greasing the pan if I’m short on parchment?

    Reply
  5. Julie says

    October 7, 2018 at 9:26 pm

    I’ll always take a cookie bar over a cookie — and especially when they’re packed with so many delicious things. Oatmeal, chocolate chips, AND m&ms? Yes, please!

    Reply
  6. Nicole says

    October 7, 2018 at 5:24 pm

    These bars have my name written all over it. I love Monster Cookies, I am sure I would love these!

    Reply
  7. Nicoletta sugarlovespices says

    October 6, 2018 at 7:01 pm

    Didn’t know about monster cookies but I’m loving the idea of turning them into cookie bars. Less work and excellent result!

    Reply
  8. Renee Gardner says

    October 6, 2018 at 5:17 pm

    These bars look delicious! I never think about turning my cookies into bars, but it seems like it would be so much easter. Thanks for the oven temp tip!

    Reply
  9. Vanessa Price says

    October 6, 2018 at 1:39 pm

    I love this easy bar version of a classic cookie. My daughters love M&M’s, so I think I’ll make this with them!

    Reply
  10. Dominique | Perchance to Cook says

    October 5, 2018 at 9:25 am

    These monster cookie bars are calling my name! I love mini M&Ms in baking and I love cookies in bar form. These look really delicious!

    Reply
  11. Analida Braeger says

    October 5, 2018 at 7:48 am

    Cookie bars!!! These are the dessert that I lose count of how many I eat because they’re so delicious. Having my own recipe will be dangerous…

    Reply
  12. Georgie says

    October 5, 2018 at 7:44 am

    These look like a perfect afternoon snack with a cup of tea! I love how fun they are!

    Reply
  13. Helen Little says

    October 5, 2018 at 2:04 am

    Yum! My son would love these. And my husband. And me! 🙂 I love M&M’s and oaty biscuits are completely my thing. Thanks for the handy tips on making these, too!

    Reply
  14. Tara says

    October 5, 2018 at 1:05 am

    I can’t believe it is October already! These bars look like such a fun recipe. I’m sure they will be a hit with my family.

    Reply
  15. Colleen says

    October 5, 2018 at 12:39 am

    I’ve actually never heard of a monster cookie, but these bars look perfectly chewy and delicious. I know of a few kids who would go crazy for these! Thanks for sharing.

    Reply
  16. Adriana Lopez Martin says

    October 5, 2018 at 12:35 am

    This monster cookie bars are so much fun perfect option or Halloween! My grandson loves M&Ms, and his birthday is coming soon I will surprise him with this monster cookies and ice cream =)

    Reply
  17. Kelly Anthony says

    October 5, 2018 at 12:18 am

    These monster cookie bars look sooooo good. I wish I had one right now along with a glass of milk.

    Reply
  18. Marie says

    October 4, 2018 at 11:46 pm

    I’ve always loved M&Ms so this sweet treat is something I would love to try! These monster cookie bars look delicious!

    Reply
  19. Leigh Suznovich says

    October 4, 2018 at 8:49 pm

    Love monster cookies, this is so great to put them in bar form!

    Reply
  20. Shelley says

    October 4, 2018 at 5:41 pm

    This is such a great idea – take a beloved cookie and make it EASIER, in a quick and simple bar form! I mean, who doesn’t love monster cookies, right?!? But I’m all about making things faster and easier – this is a great solution! Terrific tips, too – about using the right oats and adjusting baking temps for different pans – so helpful!

    Reply
  21. Belle says

    October 4, 2018 at 3:02 pm

    Yum! That looks really good! I need to make some this weekend!

    Reply
  22. Paula @ I'm Busy Being Awesome says

    October 4, 2018 at 2:35 pm

    Such a tasty treat, it looks fun and delicious!

    Reply
  23. Mimi says

    October 4, 2018 at 2:34 pm

    This sounds so yummy, I need to try this recipe

    Reply

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Hi, my name is Sharon. I’m an accountant by day, risk-taking baker and food enthusiast by night. Come join me as I share my favorite recipes and test out new ones along the way!

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