M&M Cookie Bars – Soft-Baked, Festive & Fun.

If you love the flavor of a classic chocolate chip cookie but crave the thick, chewy texture of a blondie, M&M Cookie Bars are your ultimate treat. Unlike individual cookies that can sometimes dry out on the edges, these bars are baked in a single pan, which traps moisture and ensures a “soft-baked” center from edge to edge.

They are the ultimate “blank canvas” dessert—easily customized for any holiday by simply switching the color of the candies.¹

Why Bars Beat Individual Cookies

Many bakers prefer bars over traditional cookies for three main reasons:

Feature	Individual Cookies	Cookie Bars
Effort	Requires scooping and multiple batches.	One pan, one bake, no rolling.
Texture	Higher surface area means more “crunch.”	Dense and fudgy; stays soft for days.
Candy Distribution	M&Ms often roll off or melt unevenly.	Candies are suspended in a thick dough “cushion.”

Ingredients

1 cup (2 sticks) Unsalted butter, softened to room temperature²
1 cup Light brown sugar, packed (for that deep chew)³
1/2 cup Granulated sugar⁴
2 large Eggs, room temperature⁵
1 tbsp Vanilla extract (don’t be shy with it!)
2 1/4 cups All-purpose flour⁶
1 tsp Baking soda⁷
1 tsp Cornstarch (the secret to the “soft-baked” texture)
1/2 tsp Sea salt⁸
1 1/2 cups M&Ms (plus extra for pressing onto the top)
1/2 cup Semi-sweet chocolate chips (optional, for extra richness)

Step-by-Step Instructions

1. Prep and Cream

Preheat your oven to 350°F (175°C). Line a 9×13-inch baking pan with parchment paper, leaving an overhang on the sides so you can easily lift the bars out later.9

In a large bowl, beat the softened butter and both sugars until light and fluffy (about 2–3 minutes).

2. The Liquid Gold

Add the eggs one at a time, followed by the vanilla extract.

The Pro Secret: Use room-temperature eggs. Cold eggs will cause the creamed butter to seize up, leading to a lumpy dough and an uneven bake.

3. Dry Ingredients

In a separate bowl, whisk together the flour, baking soda, cornstarch, and salt. Gradually add the dry ingredients to the wet ingredients, mixing on low speed until just combined.

Fold in the M&Ms and chocolate chips by hand using a spatula.

4. The Press and Decorate

Spread the dough into the prepared pan. It will be thick, so use a spatula or lightly greased hands to press it into the corners.

The Visual Finish: Press a handful of extra M&Ms directly into the top of the dough. This ensures they don’t get buried and makes the bars look professionally “festive.”

5. The Under-Bake

Bake for 20–25 minutes.

The Goal: The edges should be a light golden brown, but the center should still look slightly “underdone” or soft.
The Cool-Down: Let them cool completely in the pan for at least 1 hour. The residual heat will finish cooking the center while keeping it soft.

Flavor and Texture Notes

These bars are buttery, dense, and nostalgic. The brown sugar and vanilla create a “toffee-like” base that perfectly complements the milk chocolate of the M&Ms.

Texture-wise, the cornstarch is the unsung hero; it breaks up the gluten in the flour to give you a “melt-in-your-mouth” crumb that stays soft for 3–4 days. The candies provide a colorful, satisfying “snap” against the pillowy dough.

Seasonal Variations

One of the best things about this recipe is how “festive” it can become with one simple swap:

Holiday	M&M Color Choice	Extra Addition
Valentine’s Day	Red, Pink, White	White chocolate chips
St. Patrick’s Day	Green, Yellow	Mint extract (1/2 tsp)
Halloween	Orange, Purple, Brown	Pretzels for a salty crunch
Christmas	Red and Green	A sprinkle of sea salt on top

Tips and Variations

The Fudgy Version: If you want them even denser (more like a brownie), replace one of the whole eggs with two egg yolks.
Brown Butter: Melt the butter and cook it until it turns amber and smells nutty before mixing. This adds a sophisticated “toasted” flavor to the bars.
Storage: These stay soft in an airtight container for up to 5 days. You can also freeze individual squares for a quick snack later.
The “Clean Cut”: To get perfectly straight edges, wait until the bars are completely cold, then lift the parchment paper out of the pan and slice with a long serrated knife.

FAQ

Can I use a different size pan?

Yes. If you use an 8×8 or 9×9 pan, the bars will be much thicker. You will need to increase the bake time to 30–35 minutes.

Why did my M&Ms crack?

This is usually caused by the candies expanding in the heat. To minimize this, don’t overbake the bars. A few cracks are normal and add to the “homemade” charm!

Can I use Peanut M&Ms?

Absolutely, though the bars may be slightly bumpier on top. I recommend a mix of Mini M&Ms and regular ones for the best texture.

Conclusion

M&M Cookie Bars are the ultimate low-stress, high-reward dessert. They bring a pop of color to any table and are guaranteed to be the first thing gone at a potluck or party.

Would you like me to suggest a recipe for a “Marshmallow Frosting” to swirl on top of these, or perhaps help you find a “Healthy Chickpea” version of this bar for a high-protein snack?