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.

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!

stack of Peanut Butter Cookie Bars

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.

More Cookie Bar Recipes

Yield: 16 2-inch bars

Peanut Butter Cookie Bars

Prep Time 15 minutes
Cook Time 30 minutes
Total Time 45 minutes

These Peanut Butter Cookie Bars are so simple and versatile. Just stir in your favorite add-ins!

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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Peanut Butter Cookie Bars

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