Peanut Butter Cookie Bars

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!

These Peanut Butter Cookie Bars are so simple and yummy. They're versatile, too. Just stir in your favorite add-ins!

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.

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.

Peanut Butter Cookie Bars

Prep Time: 15 minutes

Cook Time: 30 minutes

Yield: 16 2-inch bars

Peanut Butter Cookie Bars


  • 1 & 1/4 cups all-purpose flour
  • 1/2 teaspoon baking powder
  • 1/2 teaspoon salt
  • 1/2 cup unsalted butter, softened
  • 1/2 cup granulated sugar
  • 1/2 cup packed light brown sugar
  • 1 cup peanut butter (smooth or crunchy)
  • 1 large egg
  • 1 teaspoon vanilla extract
  • 3/4-1 cup Peanut Butter M&Ms


Preheat oven to 350°. Lightly grease an 8-inch square baking pan.

Whisk together flour, baking powder, and salt. Set aside.

Using an electric mixer on medium speed, beat butter, sugar, and brown sugar until light and fluffy. Add peanut butter and mix well. Mix in egg and vanilla.

Reduce mixer speed to low. Gradually add flour mixture, mixing until almost blended. Stir in M&Ms.

Transfer batter to prepared pan. Bake 25-30 minutes, or until edges are lightly browned and a pick inserted into the center comes out with a few moist crumbs. Cool in pan on wire rack before cutting into bars.

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  1. Tahnycooks January 1, 2013 Reply

    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. Pam January 2, 2013 Reply

    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. Noelle January 4, 2013 Reply

    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. MrsSlik May 7, 2015 Reply

    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. Amber December 7, 2015 Reply

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

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