Monster Cookie Bars

Monster Cookie Bars are a quick and easy big batch dessert recipe that can be made in one bowl! They are just like a giant Monster Cookie. Loaded with chocolate chips and M&Ms. This bar recipe is soft, chewy and always a hit. Perfect for potlucks, bake sales and more!

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The only thing better than cookies are cookie bars! I don’t know about you, but skipping the rolling and just baking the cookie dough in a pan before you slice and serve them is my kind of baking. When I need a last-minute dessert for a party or potluck more often than not I make a batch of cookie dessert bars like these Monster Cookie Bars.

These cookie bars have pretty much all of my favorite cookie things – peanut butter, oats, and chocolate all baked up together. You can make a huge batch of these cookies in about 20 minutes start to finish… yes, you read that right!

If you’ve been following along, you know how I love my cookie bars! These Monster Cookie Bars are loaded with M&Ms and chocolate chips just like regular monster cookies, but so much easier. It’s as easy as mixing the dough and baking in a big pan! Just like my Pizza Bars, Sugar Cookie Bars and Banana Bars these Monster Cookie Bars are great when you need cookies for a crowd.

And there’s more good news – you only need one bowl to make them! Just one bowl and a mixer is all you need to make a batch of these soft and chewy cookies.

What do I need to make these bars?

If you’d rather skip my (very helpful, I think) tips and tricks, essential cooking info, and similar recipe ideas – and get straight to this delicious Monster Cookie Bar recipe – simply scroll to the bottom of the page where you can find the printable recipe card.

• Softened butter
• Eggs
• White sugar
• Vanilla
• Corn syrup
• Baking soda
• Brown sugar
• Peanut butter
• Quick oatmeal
• Chocolate chips
• M&Ms

How do I make them?

Step by Step Photos Above!

• Cream – Mix the butter and sugar together until creamy. (Photo 1 & 2)
• Mix – Add the vanilla, corn syrup, and baking soda and mix to combine. Add the peanut butter and oatmeal and mix it again. Mix in the chocolate chips and M&Ms. (Photo 3 & 4)
• Bake – Press the cookie dough into a greased 13×18″ pan. Bake the cookie bars for 15 minutes at 350°F. Cool the cookie bars fully before slicing and serving.

Tips and Tricks for the BEST Monster Cookie Bars!

• You only need one bowl to make the cookie dough, but be sure to add the ingredients in the order listed! You want to start with the butter and sugar so plenty of air gets incorporated into the mixture, so don’t add the other ingredients until the butter and sugar is light and creamy.
• Speaking of butter, it’s a lot easier to start with room temperature butter. Leave the butter out for several hours before making the cookies and you won’t have any trouble creaming it with the sugar.
• Be sure to use quick oats for this recipe, which is a faster cooking oatmeal. If you use old fashioned oats (also known as rolled oats) or steel-cut oats the cookie texture won’t be the same. If you don’t have quick oats, you can break down old fashioned oats in a food processor and they will work fine. Just pulse them a few times.
• When you press the dough into the pan press it just enough so it’s in the pan, but not too hard otherwise your cookies will be too dense. Use a light hand for this step!
• The cookies don’t have to bake long and they won’t look done when you pull them out of the oven, which is what you want for soft and chewy cookies, just like these Peanut Butter Chocolate Chip Bars. They will continue to bake and set up as they rest in the pan.
• Wait until the cookie bars are completely cooled before you slice them. The cookies may fall apart if you slice them while they’re warm.
• Once your Monster Cookies are completely cooled you can slice them and store them in an airtight container.
• These cookie bars will keep well at room temperature for up to three days as long as you keep them tightly wrapped or in an airtight container. Or, you can keep them in the refrigerator for up to a week. They won’t be as soft if they’re cold, so leave them out at room temperature before serving them.
• You can freeze these these bars! First, make sure the cookies are cooled before freezing them. Transfer them to an airtight container and freeze them for up to three months. To thaw, just leave them out at room temperature.

Other mix-in suggestions!

• Milk Chocolate Chips
• Dark Chocolate Chips
• White Chocolate Chips
• Chopped Peanut Butter Cups
• Chopped Heath Bars
• Reese’s Pieces
• Peanut Butter Chips
• M&Ms
• Nuts – Chopped Walnuts, Pecans or Almonds

More easy dessert bar recipes!

If you are like me, you’d rather make a big batch of bars than individual cookies. Here are my favorite go-to recipes!

• No Bake Peanut Butter Cereal Bars – No Bake Bars with Cheerios, Rice Krispies, M&M’s, Peanuts that are Perfectly Ooey & Gooey!
• Knock you Naked Bars – Caramel Cookie Bars with an amazing layer of gooey caramel stuffed in between the layers with a hint of peanut butter.
• Banana Bars – Topped with cream cheese frosting and so soft and tender!
• M&M Chocolate Bars – Layers Of Oats, A Sweetened Condensed Milk And Chocolate Center Topped With More Oats And M&Ms.
• Chewy Brown Butter M&M Blondies – An easy cookie bar that’s loaded with chocolate M&M candies.

WATCH THE STEP BY STEP VIDEO FOR THIS RECIPE BELOW:

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Did you make this? If you snap a photo, please be sure tag me on Instagram at @julieseatsandtreats or #julieseatsandtreats so I can see your yummy treat!

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5 from 9 votes

Monster Cookie Bars

Monster Cookie Bars ~ Soft, chewy bars stuffed full of peanut butter chips and M&M's!

Prep:10 mins

Cook:15 mins

Total:25 mins

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Ingredients

• ▢ 1/2 c. butter softened
• ▢ 3 eggs beaten
• ▢ 1 c. white sugar
• ▢ 1 tsp vanilla
• ▢ 1 tsp corn syrup
• ▢ 2 tsp baking soda
• ▢ 1 c. brown sugar
• ▢ 1 1/2 c. peanut butter
• ▢ 4 1/2 c. quick oatmeal
• ▢ 6 oz. chocolate chips
• ▢ 6 oz M&M's

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Instructions

• 1. Mix butter and sugars together.
• 2. Add eggs, vanilla, corn syrup, and baking soda. Sir in peanut butter. Stir in oatmeal. Add chocolate chips and M&M's
• 3. Bake in a greased 13×18 inch pan at 350 degrees for 15 minutes for a soft, chewy bar. They will not look done, but will cook as they set.

Tips

Tips and Tricks for the BEST Monster Cookie Bars!

• You only need one bowl to make the cookie dough, but be sure to add the ingredients in the order listed! 
• Start with room temperature butter.
• Be sure to use quick oats for this recipe. If you don't have quick oats, you can break down old fashioned oats in a food processor and they will work fine. Just pulse them a few times.
• When you press the dough into the pan press it just enough so it's in the pan, but not too hard otherwise your cookies will be too dense.
• The cookies don't have to bake long and they won't look done when you pull them out of the oven, which is what you want for soft and chewy cookies. They will continue to bake and set up as they rest in the pan.
• Wait until the cookie bars are completely cooled before you slice them. The cookies may fall apart if you slice them while they're warm.
• Once your Monster Cookies are completely cooled you can slice them and store them in an airtight container.
• These cookie bars will keep well at room temperature for up to three days as long as you keep them tightly wrapped or in an airtight container. Or, you can keep them in the refrigerator for up to a week. They won't be as soft if they're cold, so leave them out at room temperature before serving them.
• Yes, you can freeze these Monster Cookie Bars! First, make sure the cookies are cooled before freezing them. Transfer them to an airtight container and freeze them for up to three months. To thaw, just leave them out at room temperature.
• If you want to switch things up try using milk chocolate chips or dark chocolate chips. Or, add some white chocolate chips! You can also use chopped up chocolate candy like peanut butter cups or Heath bars in place of the M&Ms. If you love nuts, try adding some chopped walnuts, pecans or almonds.

Video

Nutrition Information

Calories: 532kcal (27%), Carbohydrates: 72g (24%), Protein: 16g (32%), Fat: 22g (34%), Saturated Fat: 9g (56%), Cholesterol: 38mg (13%), Sodium: 298mg (13%), Potassium: 356mg (10%), Fiber: 6g (25%), Sugar: 33g (37%), Vitamin A: 185IU (4%), Calcium: 56mg (6%), Iron: 3mg (17%)

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We are not dietitians and recommend you seek a nutritionist for exact nutritional information. The information in the nutrition box is calculated through a program and there is room for error. If you need an accurate count, I recommend running the ingredients through your favorite nutrition calculator.