If you’ve ever walked out of Costco with that big, buttery bag of marshmallow crispy cookies and thought, “I wish I could make these at home…” you’re in the right place. These cookies are everything you love about a Rice Krispie treat wrapped inside a caramel-browned butter cookie. Crispy on the edges, chewy in the middle, and loaded with toasted sweetness honestly, they’re even better fresh from your own oven.

Let’s be honest: part of the fun is in that first bite the crunch, the gooey marshmallow pull, and the nostalgia of childhood cereal mornings meeting adult-level baking flavor.

Ingredients You’ll Need

For the Cookie Dough:

½ cup (113 g) salted butter — browned
¾ cup (165 g) light brown sugar
½ cup (100 g) granulated sugar
1 large egg, room temperature
1 teaspoon pure vanilla extract (or vanilla paste for extra depth)
¾ teaspoon sea salt
½ teaspoon baking soda
1 cup (140 g) all-purpose flour (spooned and leveled)
1½ cups (43 g) Rice Krispies cereal
⅔ cup (30 g) mini marshmallows
Flaked sea salt — for topping

Optional Mix-Ins:

¼ cup mini chocolate chips for a s’mores twist
2 tablespoons extra flour for thicker, puffier cookies

Step-by-Step Instructions

1. Brown the Butter

Melt the butter in a light-colored saucepan over medium heat. Stir continuously — it’ll foam, then turn golden with a nutty aroma. Once brown specks appear, immediately remove from heat and pour into a heat-safe bowl. Chill for about 10 minutes (fridge or freezer) until slightly firm but not solid.

2. Make the Dough

Whisk together the browned butter, brown sugar, and white sugar until combined. Add the egg and vanilla, mixing until the mixture looks smooth and glossy — about 30 seconds.

3. Add the Dry Ingredients

Gently fold in flour, baking soda, and salt until no dry streaks remain. Do not overmix — this keeps the cookies tender.

4. Fold in the Good Stuff

Add Rice Krispies first, then mini marshmallows. The dough will feel a bit sticky; that’s perfect for chewy centers.

5. Scoop & Bake

Preheat oven to 350°F (175°C). Line a baking sheet with parchment paper.
Scoop 3-tablespoon-sized dough balls (about 4–5 per tray since they spread). Bake for 10–13 minutes, or until the edges are golden and the centers are just set.
If marshmallows leak out and cause uneven edges, use a spoon to gently nudge the cookies back into a round shape while warm.

Sprinkle lightly with flaked salt right after baking.

Tips & Tricks for Perfect Texture

Watch the butter: Once browned butter turns dark, it’s gone — keep stirring and sniffing for that nutty, toffee aroma.
Prevent flat cookies: Add 2–3 tablespoons of extra flour or chill the dough for 30–60 minutes.
Don’t overbake: Pull them out when edges are light golden. They’ll set as they cool.
Shape repair hack: Use a round cookie cutter to “scoot” warm cookies into perfect circles.
Brown butter bonus: Browning the butter caramelizes milk solids, adding rich, toffee-like flavor that balances the sweetness of marshmallow.

Flavor Variations & Add-Ins

Try one of these easy twists to reinvent the Costco copycat cookie:

Chocolate-Dipped: Half-dip cooled cookies in melted dark or milk chocolate.
S’mores Edition: Add crushed graham crackers and chocolate chips.
Holiday Remix: Toss in crushed peppermint or drizzle with white chocolate.
Nutty Crunch: Fold in chopped pecans or almonds for a toasty finish.

Each version keeps that chewy-crispy base but adds its own personality.

Storage & Freezing Tips

Room Temperature: Store in an airtight container up to 3 days.
Fridge Dough: You can refrigerate dough for up to 1 week before baking.
Freezer: Freeze baked cookies or dough balls for up to 3 months.
To Bake from Frozen: Bake at 325°F (160°C) for a couple of extra minutes until edges turn golden.

Pro tip: Pop leftover cookies in a 300°F oven for 2–3 minutes to re-crisp the edges.

FAQ

Why did my cookies spread too much?

Likely because the butter was too warm or the dough too soft. Next time, chill dough for 30 minutes or add an extra tablespoon or two of flour.

Can I use unsalted butter instead?

Absolutely — just add an extra ¼ teaspoon of salt to balance flavor.

Do these taste exactly like Costco’s?

Pretty close — but fresher, richer, and with more chew from the browned butter base. Most readers say these beat Costco’s hands down.

Can I make these gluten-free?

Yes — use a 1:1 gluten-free baking blend and ensure your Rice Krispies are certified gluten-free.

Nutrition Information (per cookie)

Calories: 202 kcal
Carbs: 32 g
Protein: 2 g
Fat: 8 g (5 g saturated)
Cholesterol: 33 mg
Sodium: 261 mg
Sugar: 22 g

Final Thoughts

There’s something magical about recreating a store favorite especially when it turns out better. These Marshmallow Crispy Cookies are that perfect meeting point of nostalgia and kitchen confidence. You don’t need to chill the dough or fuss with special ingredients just a few simple steps and a little butter alchemy.

Next time someone says, “They taste just like Costco’s,” smile and hand them another. You’ll both know the truth.

If you make these, share your version below — because homemade wins every time.