These irresistible cookie bars are known around here as Molly Beth Bars. They’re thick, soft bars filled with the trifecta: peanut butter, chocolate, and oats. This easy dessert recipe is an instant hit with both kids and adults alike!

Sliced chocolate chip bars with knife next to them.

These cookie bars have withstood the test of time. They’re a classic family favorite, and they were the FIRST EVER recipe post on Fork in the Kitchen. HELLO, NOSTALGIA.

The photos have since been updated (thank goodness for growth, am I right?!) but the recipe is the same as the day my mom first made them, and they’re still every bit as delicious.

Since their first appearance, the world has enjoyed Molly Beth Bars for potlucks, weeknight sweet tooth cravings, holiday desserts, sleepover parties, and more. If you’ve made your way here from those original images on Pinterest, just know these are the same bars we’ve all fallen in love with.

Regardless of what your childhood was like, I’m willing to take a gamble that the combination of gooey peanut butter, melty chocolate, and chewy oats is going to take you immediately to your kid-favorite happy place.

These cookie bars just do that to you.

Server holding up a chocolate chip peanut butter cookie bar in the air.

They’re the combination of ultimate comfort, sweet-tooth-fix, and childhood favorites.

They’re addictingly delicious.

They’re a dream come true.

Yes, yes they are. You know, I know it, and there’s absolutely no denying it.

Overhead view of cookie bars with chocolate chips next to milk jug.

While this classic combination of peanut butter and chocolate needs just about zero words, there is a little history I must share. A history to be told for posterity’s sake, as this was the first Fork in the Kitchen recipe and it holds so many dear memories. So there’s no way I’m leaving out the origin story for Molly Beth Bars (their actual name). Without further ado…

The Story Behind Molly Beth Cookie Bars

As mentioned, these cookie bars are a classic family favorite.

I’m talking as much a part of my childhood as the classic peanut butter and jelly. As much as ice cream cones on hot summer nights, as much as – no, actually more than – chocolate chip cookies.

Even before my time, they were a family tradition. My mom’s older sister, Mandy, had a recipe from somewhere along the lines during her time in girl scouts. As it evolved over the years, no one could remember the actual name of the recipe, and we referred to them as Mandy Bars in the beginning.

Close up of uncut chocolate chip cookie bars on cooling rack.

That is, until I was in high school when I was eating these bars on a regular basis.

My mom continued to update the recipe for the bars over the years. As in, she added heaping amounts of peanut butter and chocolate chips each time my brother and I begged politely asked her to make them. Because how could you not add just a little more goodness to something already amazing?

Thus, grew the name Molly Beth Bars, after my mom and her spin on the recipe, and her now-famous cookie bar legacy.

Back then, there was a period of time when these bars were made weekly, only to maybe last to the next day. 

Sliced bar with melted chocolate.

Luckily, I would often dig into a warm pan of gooey, melty bars after hours of dance practice, which made me feel like I could justify downing half of a pan in one sitting.  No joke.

Unfortunately, those dance days are long gone, but I have this magic power of justifying sitting down with a pan of warm Molly Beth Bars and a fork, all to myself. It’s what I like to call “self-care”.

Late-night chocolate chip peanut butter cookie bar cravings, here I come!

Disclaimer: once you make these for dessert, you will not be able to stop.

You will especially not be able to resist because they are so dang easy to make. One mixing bowl, an electric mixer, and a spatula later, you’ll have these indulgent bars baking away in the oven. Don’t even want to use an electric mixer? Go ahead and use a whisk and some muscles. I got you.

Whole pan of bars on cooling rack.

The simple ingredient list goes like this:

  • butter
  • flour
  • granulated and brown sugar
  • baking soda
  • vanilla
  • egg
  • creamy peanut butter
  • oats
  • chocolate chips

You will notice the word heaping gets used a lot. That’s because the beauty of this recipe is that you definitely want to overflow the peanut butter and chocolate chip measuring cups.

That is not a science. No, that’s an art, and my friends, the more the better. Which is exactly why I haven’t updated the recipe to say what ‘heaping’ might be, because friends, you’ve got to follow your gut on that part.

Three bars on top of each other with melted chocolate.

The hardest part is waiting for the peanut butter oatmeal chocolate chip bars to cool ever so slightly so they don’t crumble apart.

This may or may not work for me. I give you full permission to dig in and eat the crumbles with a fork, bar be gone until later (when you’re ready for round two).

Yes, you’ve been warned, eat these babies just warm out of the oven and you have my full permission to indulge freely.  No judgment here for consuming more than what others may deem as “socially acceptable”. In fact, what is “socially acceptable” when it comes to these babies? It is, in fact, digging straight in.

Overhead bars spread around with one on its side showing gooey chocolate next to a knife.

Seriously, make them and you’ll understand.  When it comes to these bars, you cannot go wrong.  Unless of course, you’re not eating them.  Then that’s nearly a sin.

Frequently Asked Questions

Can I double this recipe?

By golly you’ve got the right idea. Yes, you can double this recipe and make the bars in a 9×13 pan, just watch the bake time as they may be done a little sooner.

Can I use an alternative flour?

I haven’t tested it myself and wouldn’t necessarily recommend using almond or coconut flour. You may be able to use 1:1 gluten-free flour if needed. If you do, I’d love to hear how they turn out!

Can I add anything else to these cookie bars?

Yep, you can play around with add-ins. Many people have reported that they’ve added nuts to the batter and enjoyed it. M&Ms or peanut butter chips are other favorites! Flaky sea salt on top is another game changer.

How do you store the bars?

Store the bars covered, or in an airtight container, at room temperature.

Do I have to share?

No, no you do not have to share. 🙂

More Dessert Bar Recipes

If you love easy recipes, ones that include sugar specifically, you’ve gotta check these out, too!

Did you make this recipe? Please leave a star rating and review in the form below. I appreciate your feedback, and it helps others, too!

overhead bars spread around with one on its side showing gooey chocolate next to a knife
5 (26 ratings)

Get the Recipe Molly Beth’s Chocolate Peanut Butter Oatmeal Cookie Bars

Prep: 10 minutes
Cook: 20 minutes
Total: 30 minutes
Servings: 9 large bars
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An indulgent cookie bar filled with peanut butter, chocolate, and oatmeal. Guaranteed to make you reach for more (and possibly not even share!).

Ingredients

  • 1/2 cup butter, softened at room temperature
  • 1/2 cup brown sugar
  • 1/2 cup granulated sugar
  • 1 egg, room temperature
  • 1/2 heaping cup creamy peanut butter
  • 1/2 teaspoon vanilla extract
  • 1 cup all-purpose flour
  • 1/2 teaspoon baking soda
  • 1/4 teaspoon salt
  • 1 cup old-fashioned oats, rolled oats
  • 1.5 heaping cups chocolate chips*

Equipment

Instructions
 

  • Pre-heat the oven to 350° F. Line an 8×8 pan with parchment paper.
  • In a large mixing bowl, using an electric mixer, combine the butter, brown sugar, and granulated sugar. Add egg, peanut butter, vanilla extract, flour, baking soda, and salt until just combined. Stir in the oatmeal and chocolate chips.
  • Spread the dough evenly in your pan. Top with additional chocolate chips as desired for looks – and, chocolate! Bake for 18-22 minutes until edges are set and begin to just turn golden brown. The middle will be slightly jiggly, but that's what you want. The bars are like cookies in that you don't want them overbaked, with a slightly gooey center. If you prefer them more well done, bake for an additional 5-7 minutes.
  • Place the pan on a cooling rack and let it cool at least 15-20 minutes before serving so they have time to set up. The longer you let them cool, the more set they will be. However, they're just so so good when enjoyed warm that I often will eat them warm with a fork instead of "bar form".
  • The bars are excellent served with ice cream or on their own. Store any leftovers covered at room temperature.

Notes

  • I like to use milk chocolate chips in these bars, however, semi-sweet or a combination of the two are just as delicious!
  • You can use a 9×9 pan, the bars just won’t be quite as thick. Reduce baking time slightly if doing so.
Calories: 272kcal, Carbohydrates: 40g, Protein: 3g, Fat: 11g, Saturated Fat: 7g, Trans Fat: 1g, Cholesterol: 45mg, Sodium: 227mg, Potassium: 74mg, Fiber: 1g, Sugar: 23g, Vitamin A: 342IU, Calcium: 23mg, Iron: 1mg
Course: Dessert
Author: Becca Mills
Cuisine: American
Did you make this recipe?Please leave a star rating and review in the form below. I appreciate your feedback, and it helps others, too!

This post was originally FITK’s first post on March 22, 2015. The photos and text were updated in November 2019, but no changes were made to the recipe.