Name: M&M Cookie Bars
Prep time: 10 min
Cook time: 20 min
Total time: 30 min
Yield: 24 servings
Cuisine: American
Ingredients: 2.75 cup all-purpose flour; 1 tsp cornstarch; 1 tsp kosher salt; 0.75 tsp baking soda; 0.5 tsp baking powder; 1 cup unsalted butter (at room temperature); 1.25 cup packed light brown sugar; 0.5 cup granulated sugar; 2 large eggs; 1 tbsp pure vanilla extract; 1.25 cup m&m's (divided); 0.75 cup semi-sweet chocolate chips; flaky sea salt (for sprinkling on bars)

These soft and chewy M&M cookie bars are the ultimate easy dessert. No chilling, one bowl, loaded with M&Ms and chocolate. Perfect for parties! Get the recipe.

M&M cookie bars have become my go to for bake sales and game day parties. The sturdy dough presses into a single pan, so there is no scooping or chilling required. Every bite gives you soft, buttery cookie with pockets of melted chocolate and a satisfying crunch from the candy shells. A sprinkle of flaky sea salt on top balances the sweetness perfectly, making it impossible to stop at just one square.

One bowl, no stand mixer needed if you use a hand mixer or strong spatula. The dough comes together in minutes.
No chilling required. Press the dough into the pan and bake right away.
Easily customizable. Swap the M&M color to match any holiday or event.

Cornstarch, This is the secret to the soft texture. It tenderizes the dough and prevents the bars from spreading too much. No substitute works quite as well, but you can omit it and add 1 tablespoon more flour if needed.
Unsalted butter, Using unsalted butter lets you control the salt level. Make sure it is at room temperature, so it creams evenly with the sugars. If you only have salted butter, reduce the added salt to 1/2 teaspoon.
M&M candies, Classic milk chocolate M&Ms work perfectly, but feel free to use peanut, dark chocolate, or seasonal colors. Avoid the pretzel or crispy varieties as they lose their crunch during baking.

9×13 inch baking pan
Parchment paper
Stand mixer or large bowl with hand mixer
Whisk
Offset spatula or greased hands for pressing dough

Let your butter sit out until it softens to room temperature. If it is too cold, the sugar won’t cream properly and the bars can turn out dense. When you mix the dry ingredients into the wet, stop as soon as the flour disappears. Overworking the dough develops too much gluten, which makes the bars tough instead of tender.

To help the dough spread evenly, I like to use a piece of wax paper or lightly greased hands to press it into the pan. That way nothing sticks. Check the bars at 20 minutes. The edges should look set and lightly golden, but the center may still look a little soft. That’s exactly what you want.

The cornstarch in this recipe is not a mistake. It inhibits gluten formation and keeps the bars soft and chewy. If you are out of cornstarch, you can substitute with an extra tablespoon of flour, but the texture will be slightly less tender.

Let the bars cool completely in the pan before lifting them out. Warm bars are very fragile and can fall apart. If you want to speed up cooling, place the pan on a wire rack and let it sit for at least an hour before cutting. For clean squares, use a sharp knife and wipe it clean between cuts.

One of the best things about this recipe is how easily you can dress it up for any occasion. For Christmas, swap in red and green M&Ms. Pastel M&Ms are perfect for Easter, while red, white, and blue ones work great for the Fourth of July. Halloween M&Ms with orange and black candies make a spooky fall treat. You can also switch the M&M flavor itself: try peanut butter, dark chocolate, or caramel filled M&Ms for a different twist. And don’t stop at the candies, swap the semi sweet chips for milk chocolate or dark chocolate chips, or leave them out entirely for a bar that is all about the M&Ms.

These bars are fantastic on their own, but a scoop of vanilla ice cream turns them into a full blown sundae. I also like to drizzle a little caramel sauce over the top just before serving. For parties, cut the bars into small bite sized squares and arrange them on a platter. They pair well with a cold glass of milk or a hot cup of coffee.

Store the cooled bars in an airtight container at room temperature. They will stay fresh for up to 4 days. If your kitchen runs warm or humid, place a piece of parchment between the layers to keep them from sticking together.

To freeze, cut the cooled bars into squares and arrange them in a single layer on a baking sheet. Freeze until firm, about 1 hour, then transfer the frozen squares to a freezer bag or airtight container. Label with the date and freeze for up to 2 months. When you are ready to eat, let them thaw at room temperature for about 30 minutes. You can also warm individual bars in the microwave for 10 to 15 seconds if you like them soft.

For a just baked texture, reheat the bars in a 300°F oven for 5 minutes. If you only want to warm one square, pop it in the microwave for 10 to 15 seconds. Be careful not to overheat, or the chocolate can get too melty.

M&M Cookie Bar Recipe FAQs

Can I use salted butter instead of unsalted?

Yes, but reduce the added kosher salt to 1/2 teaspoon. The bars will still taste great, just a bit saltier.

Can I use all-purpose gluten free flour?

Most gluten free all purpose blends will work, but the texture may be slightly more crumbly. Add 1/4 teaspoon xanthan gum if your blend does not include it.

Why did my bars turn out hard?

Overbaking is the most common cause. Pull the bars out when the edges are set and the top is lightly browned, even if the center looks a bit underdone. Also, overmixing the dough can lead to a tougher texture.

Can I use mini M&Ms?

Absolutely. Mini M&Ms distribute more evenly throughout the dough, so you get candy in every bite. You may want to use a full 1 1/4 cups of minis since they take up less volume.