These marshmallow crispy cookies combine everything you love about a Rice Krispies treat with the texture and comfort of a thick, chewy cookie. Crispy rice cereal and mini marshmallows get folded into a buttery brown sugar dough so each bite delivers that signature snap, crackle, pop along with soft, gooey pockets of melted marshmallow. If you’ve tried the popular Costco-style marshmallow crispy cookie, this homemade version will taste familiar—and is easy to make at home.
Copycat Costco Rice Krispie Cookies
These cookies became a viral sensation for a reason: they offer the nostalgia of a cereal bar wrapped up in cookie form. The balance of granulated and brown sugar is key—granulated sugar helps create crisp edges and good spread while brown sugar (with its molasses content) contributes moisture, chewiness, and a rich caramel note. The result is a cookie that browns nicely while remaining soft and tender inside.
Freeze Your Marshmallows to Prevent Spreading
For distinct, gooey marshmallow pockets rather than large melted puddles, freeze the mini marshmallows for 15–20 minutes before folding them into the dough. This keeps them from melting too quickly and helps them maintain shape after baking.
How to Make Marshmallow Crispy Cookies
The method mirrors a classic chocolate chip cookie with a few extra mix-ins. Whisk the dry ingredients (flour, salt, baking soda, baking powder, cornstarch) in one bowl. In another bowl, cream room-temperature butter with both granulated and brown sugar until light and fluffy, then beat in vanilla and the egg. Gradually add the dry mixture to the wet, mixing until no streaks of flour remain. Fold in the crispy rice cereal and mini marshmallows gently so you don’t crush the cereal pieces. Chill the dough for 30 minutes—this step is important to keep the cookies thick and prevent excessive spreading. Scoop and bake until the edges are golden and the centers still look soft; they’ll set as they cool.
Why use both baking soda and baking powder?
Baking soda helps the cookies spread and develop a golden brown color while baking powder gives them lift so they stay thick instead of flattening out. Cornstarch adds tenderness and helps keep the centers soft. Together these ingredients create the ideal texture for a cookie that’s crisp at the edges and plush inside.
Swaps and Substitutions
Small changes let you adapt the cookies to your pantry or flavor preferences:
- Brown the Butter: Browned butter adds a deeper, nutty flavor—cool it to room temperature before combining with the sugars. Add an extra tablespoon to compensate for evaporation.
- Unsalted Butter: If using unsalted butter, add about 1/8 teaspoon extra salt to taste.
- Add Chocolate: Stir in 1/2 cup mini chocolate chips with the cereal and marshmallows for a s’mores-like twist.
- Full-Sized Marshmallows: Quarter large marshmallows to approximate the size and distribution of minis.
- Vanilla: Pure vanilla extract works as a 1:1 substitute for vanilla bean paste.
Why did my cookies turn out thin or flat?
Thin or flat cookies usually result from overly warm butter, insufficient chilling, or expired leaveners. Make sure the butter is at room temperature (not soft or oily), chill the dough for the full 30 minutes, and verify that baking soda and baking powder are fresh.
Storage and Freezing Instructions
Store cooled cookies in an airtight container at room temperature for up to 4 days. Expect the cereal to soften over time. To freeze, lay cooled cookies in a single layer on a baking sheet until firm, then transfer to a freezer-safe bag for up to 2 months. Thaw at room temperature for 1–2 hours or microwave briefly (10–15 seconds) to re-soften marshmallow centers.
Marshmallow Crispy Cookies
Equipment
- Hand mixer or stand mixer
- Cookie scoop (2 tablespoons)
- Large rimmed baking sheet
Ingredients
- 1 1/4 cup (156 g) all-purpose flour
- 1/2 teaspoon kosher salt
- 1/2 teaspoon baking soda
- 1/4 teaspoon baking powder
- 1/4 teaspoon cornstarch
- 1/2 cup (114 g) salted butter, room temperature
- 1/2 cup (100 g) granulated sugar
- 1/4 cup (55 g) packed light brown sugar
- 1 1/2 teaspoons vanilla bean paste (or 1 1/2 tsp pure vanilla extract)
- 1 large egg, room temperature
- 1 1/2 cups (about 28 g) crispy rice cereal
- 2/3 cup (about 33 g) mini marshmallows
Instructions
- Preheat the oven to 350°F (177°C). Line a large metal baking sheet with parchment paper or a silicone baking mat.
- In a medium bowl, whisk together the flour, kosher salt, baking soda, baking powder, and cornstarch until evenly combined.
- In a large bowl with a hand mixer or in the bowl of a stand mixer, cream the room-temperature butter with the granulated and brown sugars until light and fluffy. Beat in the vanilla, then add the egg and mix until incorporated.
- Add the dry ingredients to the butter-sugar mixture in 2–3 batches, mixing and scraping the bowl between additions until no flour streaks remain. Do not overmix.
- Gently fold in the crispy rice cereal and mini marshmallows, taking care not to crush the cereal.
- Chill the dough in the refrigerator for 30 minutes. Chilling helps the cookies stay thick and prevents them from spreading too much.
- Using a 2-tablespoon cookie scoop, portion dough into balls and place 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 and centers still look soft. Remove from the oven and let cookies sit on the baking sheet until they’ve set, then transfer to a wire rack to cool completely.
Notes
If your cookies spread and lose their round shape, you can gently re-form them right after they come out of the oven by placing a round glass over the cookie and nudging it into a circle. For distinct marshmallow pockets, freeze the minis briefly before folding them in.
Nutrition
Serving: 1 cookie (about 31 grams). Nutrition information is approximate and intended as a courtesy; use your own calculator for precise values based on the actual ingredients you use.
Photographs by Meg McKeehan Photography