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Peanut Butter Cookie Bars

Peanut Cookie Bars are a simplified version of a classic cookie. And they’re jam-packed with M&Ms!

overhead view of Peanut Butter Cookie Bars on a light gray plate

I didn’t really plan on making these bars. But, they just kind of happened.

stack of Peanut Butter Cookie Bars

I made a huge mistake. The last time I ordered from, I somehow reasoned that it would be a great idea to order a bag of peanut butter M&Ms. Have you tried these? I’m generally just a peanut M&Ms kind of girl, but good heavens!

To save ourselves from just eating all of them directly from the bag, I decided to make cookies. Then, as a combination of the size of the M&Ms and my unwillingness to scoop cookies, they became cookie bars.

These bars are based on my go-to peanut butter cookie recipe (which you can see in action here and here). They’ll certainly work as cookies, although you might make them a tad bigger to accommodate the size of the peanut butter M&Ms.

overhead view of stacks of Peanut Butter Cookie Bars

And, of course, you can substitute some other equally delicious thing for the M&Ms. Any variety will work, or just use chocolate chips or some other small or chopped candy bar.

Find more cookie recipes in the Recipe Index.
Peanut Butter Cookie Bars

Peanut Butter Cookie Bars

Yield 16 2-inch bars
Prep Time 15 minutes
Cook Time 30 minutes
Total Time 45 minutes

These Peanut Butter Cookie Bars are a thick version of classic peanut butter cookies. Just stir in your favorite add-ins (like M&Ms)!

overhead view of Peanut Butter Cookie Bars on a light gray plate


  • 1 & 1/4 cups (150g) all-purpose flour
  • 1/2 teaspoon baking powder
  • 1/2 teaspoon salt
  • 1/2 cup (113g) unsalted butter, softened
  • 1/2 cup (100g) granulated sugar
  • 1/2 cup (100g) packed light brown sugar
  • 1 cup peanut butter (creamy or crunchy)
  • 1 large egg
  • 1 teaspoon vanilla extract
  • 3/4-1 cup peanut butter M&Ms (or other add-ins)


  1. Preheat oven to 350°F. Lightly grease an 8-inch square baking pan.
  2. Whisk together the flour, baking powder, and salt. Set aside.
  3. Using an electric mixer on medium speed, beat the butter, sugar, and brown sugar until light and fluffy. Add the peanut butter and mix well. Mix in the egg and vanilla.
  4. Reduce mixer speed to low. Gradually add the flour mixture, mixing until almost blended. Stir in the M&Ms.
  5. Transfer the batter to the prepared pan. Bake 25-30 minutes, or until the edges are lightly browned and a pick inserted into the center comes out with a few moist crumbs. Cool in the pan on a wire rack before cutting into bars.

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    16 Comments on “Peanut Butter Cookie Bars”

  1. We have been plagued with the evil flu in my household. This is the very first thing I finally looked at that didn’t make my stomach turn! I’m now craving these peanut butter cookies! Thank you for this recipe, it’s the light at the end of the tunnel for me! Yummy

  2. This is such a cool was to use the M&Ms.. I used them in oat meal cookies before, but this is really fun too.. and they look yummie just knowing theres PB inside.. 😀

  3. This is the reason I only order from twice a year! I just got my end of the year order, and seeing that recipe made me wish I would have ordered those peanut butter m&Ms.

  4. OH MY !!! Tried this recipe . .. And “OH ME” ! These are AMAZING !!! But my family devoured them and I must make more…. !! Thanks for taking he time to post!!

  5. These were good, but were missing something. Next time I’ll use crunchy peanut butter and more salt. Kids loved them.

  6. The bars puffed up and were dry. Maybe you meant baking soda instead of baking powder as most other similar recipes use? When mixing the butter and sugars there was no way it would become light and fluffy…not enough moisture/butter. It was much too thick to get fluffy. The bars are barely edible buy only if I put a blob on vanilla ice cream on top. Very disappointed.

    • I’m sorry you had troubles, Diane. I’ve made these many times without any problems. My first troubleshooting tips are always to check the freshness and measurements of your ingredients and the accuracy of your oven’s temperature. If you’re using natural peanut butter, that can cause some differences, too.

  7. Just tried these and they are amazing! Full of peanut butter taste. They baked up perfectly. Yum.

  8. These look amazing. Do you think you can do mini peanut butter cups?

  9. Amazing recipe – full of deliciousness! Wondering if they can be frozen after baking?

  10. These are fabulous! I bake regularly for my swim group and they rave about them. I use whole wheat pastry flour, regular chocolate chips and crunchy peanut butter and they come out delicious every time!

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