S’mores Cookie Bars

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Gooey, marshmallow-filled, chocolate-layered, graham-cracker oatmeal crumb coated S’mores Cookie Bars.

Can’t get enough of graham crackers, marshmallows, and chocolate? Us either! Try these Golden Grahams® cereal S’mores bars or S’mores cookies next!

Image of a S'mores Cookie Bars being held, showing the gooey inside.

A must-make S’mores treat!

There are few things I love more in the summer than S’mores. And since bonfires and homemade S’mores aren’t as readily available as I’d like, I’ve resorted to making as many treats as possible with plenty of chocolate, lots of marshmallows, and graham crackers.

And S’mores Cookie Bars are one of my favorite creations as of late. These bars begin with a soft, chewy, and sugary oatmeal cookie layer and are loaded with creamy milk chocolate and fluffy sweet marshmallows.

S’mores Cookie Bars ingredients

  • Butter: Use unsalted butter to perfectly control the amount of salt in the bars.
  • Light brown sugar: Pack the sugar when measuring.
  • Old fashioned oats: Avoid quick oats or steel cut oats; they won’t work in this recipe.
  • White all-purpose flour
  • Baking soda
  • Salt: It balances and intensifies flavors
  • Milk chocolate chips: We use milk chocolate because nothing screams S’mores like milk chocolate to me! That said, these bars are very sweet; if you’re concerned about sweetness use semi sweet or dark chocolate instead. 
  • Marshmallow fluff: Jet-Puffed Marshmallow Creme® (not sponsored; affiliate link) is by far my favorite fluff to use in these bars. If you don’t have access to marshmallow fluff, you can try making your own.
  • Graham crackers: No S’mores treat is complete without these iconic crackers! We crush up just 2 crackers to mix into the topping for S’mores Cookie Bars.

Process shots-- images of cookie layer being made and then put in the prepared pan, then baked, and the chocolate chips and Marshmallow Fluff being added on top. Then images of the crumble topping being put on top and baked ready to be eaten. And finally a finished shot of the s'mores cookie bars.

How to make S’mores Cookie Bars 

  1. Add melted and cooled butter to brown sugar.
  2. Mix to combine.
  3. Add in the flour, oats, baking soda, and salt
  4. Stir to form a thick cookie dough.
  5. Spread a little over half of the dough to the pan, press into an even layer, and bake.
  6. Sprinkle chocolate chips on top of the warm dough.
  7. Soften marshmallow fluff in the microwave.
  8. Spread on top of the chocolate chips.
  9. Crush 2 graham crackers and add to the remaining cookie dough.
  10. Stir to combine.
  11. Sprinkle over the marshmallow fluff and bake again.
  12. Let cool and set up, cut into bars, and enjoy.

Recipe tips

  • Wait for the butter to cool to room temperature. If you add sugar to hot or even warm butter, it will melt the sugar and cause these S’mores Cookie Bars to be greasy. 
  • Line the baking pan. These bars are sticky! Make sure to line the pan with parchment paper for easy removal.
  • Spoon and level the flour: to avoid packing too much flour into the cookie base. Watch the linked video if you need some guidance.
  • Use high-quality milk chocolate for best results. You’ll get both a better melt and better flavor. My favorite for S’mores Cookie Bars is Ghirardelli® or Guittard®. Cheaper brands can have a waxier content that is far less flavorful. 

Image of a fork taking a bite out of one of the S'mores Cookie Bars.

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S'mores Cookie Bars

5 from 4 votes
Gooey, marshmallow-filled, chocolate-layered, graham-cracker oatmeal crumb coated S'mores Cookie Bars.
Print Recipe

S'mores Cookie Bars

5 from 4 votes
Gooey, marshmallow-filled, chocolate-layered, graham-cracker oatmeal crumb coated S'mores Cookie Bars.
Course Dessert, Snack
Cuisine American
Keyword Smores Cookie Bars
Prep Time 25 minutes
Cook Time 21 minutes
Total Time 46 minutes
Servings 12 -16 bars
Calories 205kcal
Cost $5.32

Equipment

  • 8x8 or 9x9 pan (8x8 for thicker bars; 9x9 for thinner bars; we like 8x8 best!)

Ingredients

  • 3/4 cup unsalted butter, partially melted and cooled
  • 3/4 cup (150g) light brown sugar, packed
  • 1 cup (135g) white flour
  • 1 cup (102g) old fashioned oats, do not use quick or steel oats
  • 1 teaspoon baking soda
  • 1/2 teaspoon salt
  • 1 bag (12 ounces) milk chocolate chips
  • 1 jar (7 ounces) marshmallow fluff (I use Jet-Puffed Marshmallow Creme)
  • 2 graham crackers

Instructions

  • PREP: Preheat the oven to 350 degrees F. Line an 8x8 or 9x9-inch baking pan with parchment paper and set aside. We prefer 8x8 pan for thicker bars, but either pan size works.
  • COOKIE BASE: In a large bowl, mix the 3/4 cup melted and cooled butter (See Note 1), 3/4 cup brown sugar, 1 cup flour, 1 cup oats, 1 teaspoon baking soda, and 1/2 teaspoon salt. Stir until combined into a thick cookie dough. Divide the mixture in half and press one half of it into the prepared pan.
  • BAKE: Bake at 350 degrees for 8 minutes, then remove.
  • CHOCOLATE AND MARSHMALLOW: Immediately out of the oven, sprinkle the 1 bag of chocolate chips evenly over the cookie crust. Warm the marshmallow fluff in the microwave (make sure there is no metal/foil topping on the fluff or don't microwave) for 7 seconds. Spoon the marshmallow fluff on top of the chocolate chips and, working carefully (and slowly), gently smooth into one layer.
  • REMAINING COOKIE DOUGH: Crush up the 2 graham crackers (I put them both in a bag, seal the bag, and crush with a wooden spoon or handle of a knife; just a coarse crush is enough). Add the crackers to the rest of the cookie dough mixture and stir to combine. Crumble the cookie dough mixture over the marshmallow fluff. Bake for another 13-15 minutes until the top layer is lightly browned.
  • COOL: Remove from the oven and allow to cool at room temperature for at least 1 hour before cutting into the bars. Using the overhang of parchment paper, pull bars out and cut with a sharp knife. Best enjoyed within 2-3 days (store in an airtight container).

Video

Recipe Notes

Note 1: Don't add hot butter to the sugar -- it will melt the sugar and cause greasy bars.

Nutrition Facts

Serving: 16bars | Calories: 205kcal | Carbohydrates: 32.9g | Protein: 1.9g | Fat: 9.1g | Cholesterol: 23mg | Sodium: 42mg | Fiber: 1g | Sugar: 17g

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41 Comments

  1. Chelsea, that moving picture is AWESOME!! and so are these bars, obviously. Ok, you totally sold me by saying that these are your absolute favorite s’mores dessert ever!! So creative to use oatmeal. I was always one to reach for any dessert with oatmeal in it!! Pinned for sure, thanks lovely!

  2. I have really enjoyed all these s’mores week posts. Wish I could taste every single one of them! And I absolutely love your new blog design, Chelsea. 🙂 These bars look so good with that gooey marshmallow. Mmmm. 🙂 Pinned!

  3. LOVING all the s’mores recipes and the new & improved site!!! truly looks fabulous – All the best with it!!! xx

  4. 5 stars
    I LOVE the new site design! SO pretty and perfect and you!

    and girl…you made a bomb gif. I’m jealous. These bars are so insanely gooey and s’mores-y (new adjective) and just I want to eat an entire pan by myself. so yeah.

    1. Hi Rach! I haven’t tried it, but I don’t see why that wouldn’t work. You will just need to watch the baking times and adjust for a larger pan!

  5. I made these bars this weekend and they are SOOOOOOOO GOOD!!! I had to add a few minutes in the oven (4 minutes first time in the oven, 6 minutes second time in the oven) because my oven runs cooler than it’s supposed to. But other than that, I followed the recipe exactly and they were perfect. My fiance, who doesn’t like S’mores, begrudgingly took a bite because I forced him, but then proclaimed that the bars were delicious. My father stated that the bars were the best thing he’s tasted in a long time. Thank you so much for the recipe!

    1. Thank you SO much Sarah for taking the time to review these and I so appreciate all your kind words! Glad you fiance liked them – haha my husband was the same 🙂 He says he doesn’t really like s’mores desserts but loved these!

  6. Making these tomorrow morning, to take & share with friends at dinner. And a great way to use up the leftover s’mores ingredients from camping this summer! Thanks for the recipe!

  7. 5 stars
    I agree with Chelsea – my favorite S’mores dessert ever! I followed instructions exactly, and they turned out perfect. I refrigerated them after they cooled to make them easier to cut into bars. This one is a keeper. Just fantastic.

    1. Yay! So great to hear they are your favorite S’mores dessert!! Still my favorite too 🙂 Thanks for the tip about putting them in the fridge for easier slicing! And thanks for the kind comment!

  8. Hi! I’m just wondering what will happen if I sub in peanut butter instead of regular butter, then cut out sugar completely. I’ve made s’mores bars without sugar, but I used butter at that time. If I use peanut butter and a little milk, will the cookie part taste like peanut butter?

    1. I’m sorry to not be of more help, but as I haven’t tried any of those swaps in this particular recipe I really couldn’t say if they would work out like you are thinking. I do think they would taste like peanut butter if you used that in place of the butter though.

  9. I made these tonight and while tasty, the top never formed a “dough” and didn’t bake into the other layers. I followed the recipe exactly. Any thoughts?

    1. The top doesn’t really bake into the layers – it’s definitely it’s own layer that tends to mesh with the marshmallows as they get melted. I’ve never had any problems with it not baking all the way in all the times I’ve made these, so I’m not quite sure what’s going on. Did the bottom layer bake for you or was that not all the way baked either? Because that may suggest a cooler oven? Perhaps a few more minutes in the oven could bake it a little more. However, you’ll want to be careful that you don’t overcook it because the marshmallows will not be great.

  10. These look delicious! I wanted to make them ahead to bring camping this weekend. Do they keep for a couple of days? Would I have to keep them refrigerated or is room temperature okay?

    1. They actually aren’t the best after a couple of days or so just because of the marshmallow layer (gets hard and blah tasting). If you do make them ahead wrap them SUPER tightly and room temperature is fine as long as it’s not too hot they will be great 🙂 ENJOY!

  11. 5 stars
    Been making these for nearly 3 years, always a 10 from everyone. I call it Death by Bob, hope that’s ok, Chelsea the real mvp. Really is the best.

  12. I was so excited to make these. I’m new to your site and these looked incredible. Unfortunately the bottom layer was a crumbly mess. There really wasn’t anything binding it to the top 2 layers either. So, when cut, the bottom layer just fell off and all you got was the top ingredients. Did you maybe forget to write down to add an egg to the cookie dough part? That would make it softer and hold together and taste more like an actual cookie.

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