This Marshmallow Oreo Chocolate Chip Cookie Bars recipe is a chocolate dessert lover’s dream! Double chocolate chip cookies are filled with crushed Oreos and marshmallow fluff to make the ultimate gooey dessert bar.

I’m kind of obsessed with these Marshmallow Oreo Chocolate Chip Cookie Bars! I mean, can you blame me?? I mean, I’d love these double chocolate cookie bars on their own, but when you stuff them with the works?? I can’t be held responsible for inhaling these in 5 seconds flat.

All right, guys, who needs something sinfully rich, gooey and fudgy in their lives?

If you’re like me, this has been on the diet for the past 3 weeks and I don’t see that changing anytime soon.

This week in particular I needed comfort food (rather, comfort dessert 😉). It’s been a long week and one that has felt especially overwhelming. It’s been a roller coaster of emotions as of late, and if you can relate, let me tell you, these chocolate cookie bars help immensely.

They’re simple to make, mostly filled with easy-to-find ingredients (but if you’re having trouble finding any of them or don’t have them on hand, I’ll offer some substitutions down below you can use).

This is not the first cookie bar I’ve shared, and it certainly won’t be the last (cue Marshmallow Peanut Butter Chocolate Chip Cookie Bars and these Chocolate Chip Butterscotch Cookie Bars).

If I had to choose THE dessert—you know, the one I’d want if I was ever stuck on a desert island—it would be chocolate chips cookies (it just barely tops out over cheesecake, which is something I want 99% of the time too).

I love how simple cookies are, yet they have all the flavors of comfort and memories.

If possible, cookie bars are even easier to make. While these Marshmallow Oreo Chocolate Cookie Bars have a couple more steps than a basic cookie bar recipe, trust me, they are still very easy to make and very much worth it.

First things first, let’s talk about what ingredients you need for these chocolate cookie bars:

butter
brown sugar and granulated sugar
eggs
vanilla extract
baking soda, salt and espresso powder
flour
cocoa powder
chocolate chips and oreos
marshmallow fluff

For the most part, you might have all of these ingredients right in your pantry. However, let’s talk about substitutions for this marshmallow chocolate cookie bar recipe.

Let’s talk easy double chocolate cookie bar substitutions:

Sugar: If you only have granulated sugar, feel free to use all of that in place of brown sugar. If you only have brown sugar, feel free to use that in place of granulated sugar.
- Or, you can add molasses to granulated sugar to make brown sugar. Brown sugar adds more moisture to the cookies, so if you use all granulated sugar, the cookies might not be as fudgy. But, if you don’t feel like making your own brown sugar, you can certainly use all granulated sugar.
Espresso powder: This is 100% optional. Coffee enhances the flavor of chocolate, which is why I love adding espresso powder to any chocolate dessert. It’s a great way to add a lot of depth to a recipe without changing too much to the recipe. However, if you don’t have espresso powder feel free to skip it. You can use instant coffee granules as a substitute.
Chocolate Chips: You can use any chocolate chips you have on hand. I use semi-sweet, but sub in milk chocolate chips, dark chocolate, white chocolate—even peanut butter chips.
Marshmallow fluff: Marshmallow fluff makes these chocolate oreo cookie bars extra rich and gooey. Now, if you don’t have marshmallow fluff, you can use marshmallows. However, if you use marshmallows, they won’t be as gooey in the cookie bars as marshmallow fluff.
- If you use mini marshmallows, I’d use 1 cup to 1 1/2 cups, making sure they’re in a flat, even layer.
- If you use large marshmallows, I’d cut them in half and place them in a flat layer. You will probably need 1 – 1 1/2 cups as well.

Marshmallow Oreo Chocolate Chip Cookie Bars Tips & Tricks cont:

These cookie bars are meant to be gooey, so it’s important to make sure you do not over bake these double chocolate chip cookie bars. Once the cookie bars rise, the edges crisp, and the center is no longer jiggly, take them out of the oven. They might sink slightly, which is just fine.
Additionally, cocoa powder can make baked goods really dry, so you want to make sure that not only is there enough fat in the recipe (in this case, butter), but also that they aren’t over baked. I know, I know. I’ve mentioned it twice. Basically, just keep an eye on them once they are almost done!
Marshmallow cream can be difficult to work with since it is such a sticky substance. I have found that if you dip your spoon or spatula in warm water first, it helps keep the marshmallow from sticking as much.
Also, if you like a whole bunch of marshmallow cream, definitely use the whole 7 oz jar. If you want a little less, I’d suggest using 4 oz instead. They won’t be as gooey, but they do still have a rich chocolate and marshmallow flavor. (I tried it both ways. I prefer using the whole jar, but people liked them both ways!)