M&M Cookie Bars

M&M Cookie Bars!! One of my favorite desserts of all times. And also be warned - one is NOT to be left alone with a pan of these! These cookie bars are on par with my famous cheesecake cookie bars. You may want to check those out as well!

Is there anything better than a soft homemade cookie in bar form? Where the edges are just lightly golden brown and a tad bit crunchy... and the inside is gooey and soft and melts in your mouth? Let me answer that for you.... no.

It doesn't get better than cookie bars when it comes to a quick and easy dessert that literally every single person will love. These cookie bars are my favorite sugar cookie recipe baked up in bar form. You all know how I love the giant M&M cookies and these are just the perfect bar form for that perfect cookie!

Ingredients & Substitutions

Substitutions

🍫 Candy + Chocolate Swaps

• M&Ms — the classic, but any color mix works (holiday themes are always fun).
• Peanut butter M&Ms or Reese’s Pieces — for a nutty twist.
• Chocolate chips (semi-sweet, dark, or white) — mix them in or sub entirely.
• Chopped chocolate bars — for gooier pockets of melty chocolate.
• Mini candies — like chopped Snickers, Twix, or Kit Kats for a fun mashup.

🧈 Fat + Sugar Variations

• Brown butter — adds a nutty, caramelized depth.
• Coconut oil — for a dairy-free version with a hint of flavor.
• Light brown sugar — milder sweetness.
• Dark brown sugar — deeper molasses flavor and extra chew.

🥚 Flour & Texture Swaps

• All-purpose flour — classic for soft, chewy bars.
• Bread flour — for a chewier, slightly denser texture.
• Whole wheat pastry flour — adds nuttiness and fiber without heaviness.
• Gluten-free 1:1 flour blend — works great; just chill the dough before baking.

🧂 Flavor Boosters

• Espresso powder — intensifies the chocolate flavor.
• Flaky sea salt on top — makes them next-level.
• Cinnamon or nutmeg — adds warmth and depth.
• Vanilla bean paste — for a richer, aromatic flavor.

🍪 Fun Add-Ins

• Chopped nuts — pecans, walnuts, or almonds for crunch.
• Toffee bits — for caramel flavor and texture.
• Mini marshmallows — for a gooey s’mores version.
• Shredded coconut — adds chew and a hint of sweetness.

*For a full list of ingredients and instructions please see recipe card below.

How to Make M&M Cookie Bars

Step 1: Preheat the oven to 350 degrees. In a large bowl, combine the melted butter and brown sugar and mix with a wooden spoon for 1 minute until combined.

Step 2: Add the vanilla and eggs, making sure to scrape down the sides of the bowl, and mix until fully incorporated.

Step 3: Add the dry ingredients into the bowl and slowly mix until just combined. The batter will be a bit stiff, but that's normal.

Step 4: Fold in 1 cup of the Milk Chocolate M&M’s.

Step 5: Spray a 9x9 metal baking pan (see note above) with baking spray and line it with parchment paper. Spoon the batter into the prepared baking sheet and sprinkle with the remaining Milk Chocolate M&M’s and Maldon sea salt if desired.

Step 6: Transfer it into the oven. Bake for 35-40 minutes. Once the bars have baked, remove them from the oven and let cool for at least 2 hours before cutting and serving.

How to Store M&M Cookie Bars

Cut these into squares once cooled, and store in an airtight container for a few days. You can also store in the fridge to keep them longer, about two weeks.

How to Freeze M&M Cookie Bars

We have not had leftovers for these in our household! However, if you want to freeze them, store these bars in a freezer bag or airtight container for about 3 months. Defrost in the fridge or outside to serve.

🍪✨ 12 Tips + Tricks for the Best M&M Cookie Bars

• Use room-temperature butter. Soft (not melted!) butter creams better with the sugars and gives you that thick, chewy cookie-bar texture instead of something cakey.
• Don’t skimp on the brown sugar. Brown sugar adds moisture and chew. It’s what makes these bars taste rich and caramel-y. The combo of white + brown is key.
• Mix just until combined. Overmixing = tough bars. Once the flour disappears, you’re done. Fold in the M&Ms gently so they don’t crack apart.
• Line your baking dish. Parchment paper with a little overhang makes it so easy to lift out the entire slab and cut perfect squares. No sticking, no crumbling.
• Press the dough evenly. Use your hands or an offset spatula to spread the dough to the edges. Even thickness = even baking.
• Add extra M&Ms on top. Press a handful into the surface before baking so the colors stay bright and pretty, it’s the bakery-style finishing touch.
• Don’t overbake! Pull them when the center still looks slightly underdone. They’ll set as they cool and stay soft and chewy instead of dry.
• Cool completely before slicing. This is the hardest part, but it’s what gives you clean edges and bars that hold together instead of crumbling into a cookie avalanche.
• Switch up the mix-ins. Mini chocolate chips, pretzels, peanut butter chips, chopped nuts, whatever you love. M&Ms play well with others.
• Store them properly (if they last). Keep in an airtight container to maintain that soft chew. Warm them for 10 seconds if you want a gooey, fresh-from-the-oven moment.
• Use a 9x9 pan. Don't try and do it in a 9x13 or an 8x8... it won't be the same. Trust me - there's a reason I developed it this way! And a glass or ceramic baking dish doesn't retain heat the same way a metal baking dish does... so use a metal baking dish! And 8x8 (while it's the same shape is only 64 square inches and a 9x9 is 81 inches. So that will WILDLY affect baking time.
• After the baking time - LET THESE SET FOR 2 HOURS. These cookie bars might look a little under-baked but they need time to finish residual baking once they come out of the oven.

FAQs

If you tried this recipe, please leave a 🌟 star rating and let me know how it goes in the 📝 comments below. Thanks for visiting today