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These marshmallow crispy cookies take everything you love about a classic Rice Krispies treat and turn it into a thick, chewy cookie. Crispy rice cereal and mini marshmallows get folded into a buttery brown sugar dough, so every bite has that signature snap, crackle, pop—plus soft, gooey pockets of melted marshmallow. If you’ve had the Costco marshmallow crispy cookie, these will look (and taste) very familiar.
Copycat Costco Rice Krispie Cookies
If you’ve wandered through the bakery section of Costco recently, you’ve probably seen the Kirkland Signature Marshmallow Crispy Cookies. They blew up all over social media in summer 2025, and for good reason: they taste like a cookie and a cereal bar had a baby. My homemade version gives you that same crispy-gone-gooey texture, minus the drive to the warehouse.
Part of what makes this cookie so good is the sugar combo. Using both granulated and brown sugar instead of just one or the other creates a base that’s closer to a chocolate chip cookie. The granulated sugar gives you crispy edges and a great spread, while the molasses in the brown sugar adds moisture, chew, and a deeper caramel flavor. It’s the same reason my cinnamon brown sugar cookies are so soft and rich.
Freeze Your Marshmallows to Prevent Spreading
If you prefer gooey pockets of marshmallows rather than slightly crisp puddles, freeze your mini marshmallows for 15-20 minutes before folding them into the dough. They’ll melt more slowly and stay more intact.
Love marshmallows in cookies? Check out my fluffernutter cookies for a PB take!
How to Make Marshmallow Crispy Cookies
The dough for these cookies comes together just like a classic chocolate chip cookie, with a couple of fun mix-ins at the end. Whisk your dry ingredients (flour, salt, baking soda, baking powder, and cornstarch) together in one bowl. In a separate bowl, cream the butter and both sugars until light and fluffy, then beat in the vanilla bean paste and egg.
Add the dry ingredients to the wet in 2–3 batches, then fold in the crispy rice cereal and mini marshmallows by hand, taking care not to crush them. Chill the dough for 30 minutes (don’t skip this step, or your cookies will turn out thin and lacy!), then scoop and bake. They should look done on the edges, but still quite soft in the center; they’ll continue to firm up as they cool.
Why does this recipe use both baking soda and baking powder?
I know many cookies opt for one or the other, but these cookies really need both. The baking soda helps them spread and brown, while the baking powder gives them a little extra lift so they stay thick instead of turning out flat and crispy.
Alongside those two leaveners, cornstarch helps keep these cookies soft and tender in the middle rather than dense. Don’t skip it either!
Swaps and Substitutions
While I think these cookies are perfect as is, there are a few small adjustments you can make to suit your personal preferences and what you have on hand:
- Brown the Butter: For a deeper, nuttier flavor, brown the butter and let it cool to room temperature before creaming it with the sugar. You’ll want to add an extra tablespoon or so to make up for evaporation.
- Use Unsalted Butter: If you swap in unsalted butter, be sure to add an extra pinch (about ⅛ teaspoon) of salt to the recipe.
- Add Chocolate Chips: Fold in ½ cup of mini chocolate chips along with the cereal and marshmallows for more of a s’mores-adjacent spin.
- Use Full-Sized Marshmallows: Chop larger marshmallows into quarters to distribute them evenly into the dough if you can’t find minis.
- Swap the Vanilla: Pure vanilla extract works as a 1:1 substitute for the vanilla bean paste.
Why did my cookies turn out so thin/flat?
These cookies easily go from plush to lacy if you don’t take the proper precautions. That’s part of why I add baking powder and cornstarch on top of the more traditional baking soda. But if your butter’s too warm, the dough doesn’t chill for long enough, or your leaveners are expired, you may still end up with flat cookies. Make sure to chill for the full 30 minutes, and double-check that your baking soda and powder are fresh.
Storage and Freezing Instructions
Store leftover marshmallow crispy cookies in an airtight container at room temperature for up to 4 days. Keep in mind that the cereal will continue to soften as they sit. To freeze, place cooled cookies in a single layer on a baking sheet until solid, then transfer to a freezer-safe bag to store for up to 2 months. Let thaw at room temperature for 1–2 hours, or microwave for 10–15 seconds to get the marshmallows nice and gooey.
Marshmallow Crispy Cookies
Ingredients
- 1 ¼ cup (156 g) all-purpose flour
- ½ teaspoon kosher salt
- ½ teaspoon baking soda
- ¼ teaspoon baking powder
- ¼ teaspoon cornstarch
- ½ cup (114 g) salted butter, room temperature
- ½ cup (100 g) granulated sugar
- ¼ cup (55 g) packed light brown sugar
- 1 ½ teaspoons vanilla bean paste
- 1 large egg, room temperature
- 1 ½ cups (28 g) crispy rice cereal
- ⅔ cup (33 g) mini marshmallows
Instructions
- In a medium bowl, add all the dry ingredients and whisk to incorporate thoroughly.1 ¼ cup (156 g) all-purpose flour, ½ teaspoon kosher salt, ½ teaspoon baking soda, ¼ teaspoon baking powder, ¼ teaspoon cornstarch
- In a large bowl with an electric hand mixer or bowl of a stand mixer, cream butter and sugars together until light and fluffy. Add the vanilla bean paste then beat in the egg.½ cup (114 g) salted butter, ½ cup (100 g) granulated sugar, ¼ cup (55 g) packed light brown sugar, 1 ½ teaspoons vanilla bean paste, 1 large egg
- Add in the dry ingredients in 2-3 separate batches, making sure to scrape down the sides of your bowl with each addition. You want to mix until there are no more flour streaks. Do not overmix.
- Fold in crispy rice cereal and mini marshmallows.1 ½ cups (28 g) crispy rice cereal, ⅔ cup (33 g) mini marshmallows
- Place the bowl in the refrigerator to chill for 30 minutes.
- Preheat the oven to 350 °F (177 °C) and line a large metal baking sheet with parchment paper or silicone baking mat.
- Using a 2 tablespoon cookie scoop, scoop cookie dough and form into a ball and place each cookie dough ball about 2 inches apart on the prepared baking sheet.
- Bake on the middle rack for 10-11 minutes or until the edges are golden brown. Immediately remove from the oven and allow to cool on the baking sheet until they’re set. Carefully transfer to a wire baking rack to cool completely.
Notes
Nutrition
Photographs by Meg McKeehan Photography
