Soft, chewy, and LOADED with goodies, these peanut butter Monster Cookie Bars are made in one bowl and ready in under an hour. If you’re a fan of chocolate, peanut butter, and oats, you’re gonna love them!
These bars do contain flour, but if you need a gluten-free version, try my oatmeal monster cookies.
3 Tasty Cookies in 1 Bar!
If you love oatmeal cookies, peanut butter cookies, and chocolate chip cookies, these bars are for you! They even have some colorful M&M’s tossed in to make them extra fun!
Melted butter makes them nice and chewy, and the oats add a great texture. And of course with two kinds of chocolate chips plus the colorful candies, they are sure to please any chocoholic.
How to make chewy monster cookie bars:
- PREP – Melt the butter in a large bowl in the microwave. Spray a 9×13″ pan with cooking spray. Preheat your oven to 350°.
- WET INGREDIENTS – Whisk the brown sugar into the melted butter until no lumps remain. Add the eggs, peanut butter, and vanilla; whisk until smooth.
- DRY INGREDIENTS – Add the flour, baking powder, rolled oats, chocolate chips, and M&M’s. Reserve some of the chocolate chips and M&M’s to press on top of the bars.
- BAKE – Press the monster cookie dough evenly in the bottom of the prepared baking pan using wet hands. Sprinkle with chocolate chips and M&M candies. Bake at 350° for about 35 minutes, or until barely set in the middle.
- COOL – We actually enjoy these bars ooey gooey and warm, but they are easier to cut after they are completely cool. It’s up to you!
Storing leftover monster bars
These bars will last for 4-5 days at room temperature if stored in an airtight container. For maximum freshness, you can wrap them individually in plastic wrap and they will last up to a week.
You can also freeze the bars. I recommend letting them cool completely, wrapping in plastic wrap, and placing them in heavy-duty freezer bags. They will last in the freezer for 4-5 months. Let them thaw at room temperature.
PRO TIPS:
- For best results, use regular creamy peanut butter like Jif or Skippy. Natural peanut butter doesn’t work quite as well.
- If all you have is crunchy peanut butter, add an additional 1/3 cup or the bars tend to be dry.
- Before measuring peanut butter, spray your measuring cup with cooking spray and it will slide out much easier!
VARIATIONS:
- For even more peanut butter flavor, stir in chopped roasted peanuts, peanut butter chips (my favorite!), or Reese’s pieces.
- If you have leftover leftover halloween candy bars, you could chop them up and use them in place of the chocolate chips or M&M’s.
- I make these with old fashioned oats because that’s what I have on hand, but quick oats would also work.
- Need a big batch to feed a crowd? You can double the recipe and bake them in a rimmed cookie sheet. Decrease the baking time by about 10 minutes.
TRY THESE BAR COOKIES:
- Lunch Lady Peanut Butter Bars
- Sugar Cookie Bars Recipe
- Maraschino Cherry Bars
- Congo Bars
- Snickerdoodle Bars
- Oatmeal Chocolate Chip Bars
MONSTER COOKIE BARS RECIPE
Peanut Butter Monster Cookie Bars
Equipment
Ingredients
- 1 cup butter melted and slightly cooled
- 2 cups brown sugar
- 2 large eggs
- 1 cup creamy peanut butter
- 1 Tbsp vanilla extract
- 1 ½ cups all purpose flour
- ½ tsp baking powder
- 2 ½ cups old-fashioned oats
- ¾ cup semi-sweet chocolate chips
- ¾ cup milk chocolate chips divided
- 1 ½ cups M&M’s divided
Instructions
- Melt the butter in the microwave in a large glass bowl; set aside.
- Spray a 9×13" pan with non-stick cooking spray. (For easier cleanup, line the pan with parchment paper or foil first.) Preheat your oven to 350 degrees.
- Add the brown sugar to the butter and whisk until smooth. Whisk in the eggs, peanut butter, and vanilla.
- Stir in the flour, baking powder, oats, semi-sweet chocolate chips, 1/2 cup of the milk chocolate chips, and 1 1/4 cups of the M&M's.
- Press dough into the prepared pan. Sprinkle the remaining 1/4 cup of chips and 1/4 cup M&Ms on top.
- Bake at 350° for 28-35 minutes or until barely set in the middle and golden brown around the edges. For soft & chewy bars, it's better to under-bake rather than over baking.
- Let the bars cool for at least 20 minutes, but they cut more cleanly after they have cooled for an hour or two.
Notes
Nutrition
These delicious monster cookie bars are always a huge hit at potlucks, picnics, and bake sales!
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