Soft and Chewy Old-Fashioned Peanut Butter Bars are the kind of simple sheet-pan dessert I make when I want something reliable and classic. They’re thick, soft, and have that familiar peanut butter cookie flavor, but in an easy bar form.
What makes this version stand out for me is the texture: chewy edges, a tender center, and a smooth peanut butter frosting that sets up nicely so the bars slice clean. I like these a little chilled because the frosting firms up and the peanut butter flavor really comes through.
These are great for cookie trays, bake sales, and lunchbox treats, and they’re one of my favorite bars to bring to a casual get-together. They also hold up well on a platter, which I appreciate when I’m serving dessert to a group.
Why You’ll Love This Recipe
Soft and Chewy: These stay tender in the middle with just enough structure on the edges, so they feel like a real old-fashioned bar instead of a dry blondie.
Sheet Pan Simple: One pan, no scooping, no batches. I like this when I want a dessert that’s easy to portion and serve.
Peanut Butter Frosting: The creamy frosting is the best part if you ask me. It’s smooth, rich, and sets up well after a short chill.
Great for Sharing: You get a full 9×13 pan, and the bars cut into neat squares that travel well for parties and potlucks.
Easy to Switch Up: You can add chocolate chips, drizzle chocolate over the top, or swap in a little crunchy peanut butter for texture.
Ingredients You’ll Need
Peanut Butter Bars
- Unsalted butter: I use softened butter so it creams easily with the sugars. If it’s too warm and greasy, the bars can bake up heavier.
- Creamy peanut butter: Regular creamy peanut butter works best here. Natural peanut butter can be a little unpredictable and oily in bar recipes.
- Light brown sugar: This is where a lot of the chew comes from. Dark brown sugar works too if that’s what you have.
- Granulated sugar: Helps the bars set and gives a little crispness around the edges.
- Eggs: Use large eggs. They help the batter hold together and keep the center tender.
- Vanilla extract: Don’t skip it. It makes the peanut butter taste more rounded and less flat.
- All-purpose flour: I use regular flour here. Measure it carefully so the bars don’t turn dry.
- Baking soda: This gives the bars just enough lift so they’re not dense.
- Fine salt: Peanut butter desserts need salt. It keeps the flavor from tasting one-note.
Peanut Butter Frosting
- Unsalted butter: Softened butter makes a smooth frosting. If it’s still cool, it tends to stay a little lumpy.
- Creamy peanut butter: This keeps the frosting silky and easy to spread. You can swap in a bit of crunchy if you want texture on top.
- Powdered sugar: Sweetens and thickens the frosting. I like adding it gradually so it doesn’t puff everywhere.
- Milk: Use just enough to loosen the frosting. Start small, because it can go from thick to runny fast.
- Vanilla extract: A little vanilla helps the frosting taste like “dessert” instead of straight peanut butter.
- Salt: Add a pinch, then taste. I almost always add a little more than I think I need.
Recipe Instructions
- Preheat the oven: Heat the oven to 350°F. Line a 9×13-inch baking pan with parchment paper, leaving some overhang, then lightly grease it.
- Cream the butter and sugar: Beat the softened butter, peanut butter, brown sugar, and granulated sugar until smooth and fluffy.
- Add the eggs: Beat in the eggs, then mix in the vanilla until everything is combined.
- Mix the dry ingredients: Whisk the flour, baking soda, and salt together in a separate bowl.
- Add the dry ingredients: Mix the flour mixture into the wet ingredients just until you don’t see dry streaks of flour.
- Spread the batter: Spread the batter evenly in the prepared pan. Smooth the top as best you can so the bars bake evenly.
- Bake: Bake for about 18 minutes, until the edges are lightly golden and the center is set but still soft.
- Let cool: Cool the bars completely in the pan before frosting.
- Beat the frosting: Beat the butter and peanut butter until smooth.
- Add the powdered sugar: Add the powdered sugar and beat on low at first, then on medium until thick.
- Add the milk: Beat in the vanilla and enough milk (2 to 4 tablespoons) to make the frosting spreadable, then add salt to taste.
- Frost and chill: Spread the frosting over the cooled bars. Chill for 20 to 30 minutes to set the frosting, then slice into squares.
Some of my tips!
This is the part that really makes a difference. If you only read one section, make it this one because this is where I share the little trick that helps the recipe turn out so well.
Recipe Tips & Tricks
Don’t overbake the bars. Pull them when the edges look set and lightly golden, and the center looks set but still soft. They’ll finish as they cool, and that’s what keeps them chewy.
Use parchment paper. The overhang makes it easy to lift the whole slab out of the pan, which is the simplest way to get neat cuts.
Let them cool completely before frosting. If the bars are warm at all, the frosting can melt and get greasy instead of creamy.
Add milk slowly to the frosting. I start with a couple spoonfuls and only add more if I need it. It’s easy to thin it out, but hard to fix it if it gets too loose.
Stop mixing once the flour disappears. Overmixing can make the bars a little tougher. Mix just until you don’t see dry flour, then stop.
Make some touches!
There are plenty of easy ways to serve this depending on the occasion. Keep it simple, or add a few small touches to make it feel a little more special.
Serving Suggestions
- Milk: A cold glass of milk is simple and classic with peanut butter bars. It’s especially nice if you chill the bars first.
- Coffee: These are really good with coffee, especially if you like your coffee not too sweet. I usually go for a plain drip coffee or an americano.
- Ice cream: Serve a bar with vanilla ice cream on the side if you want a more “dessert plate” feel. A little chocolate sauce on the ice cream is good with the peanut butter frosting.
- Fruit: Strawberries or raspberries are nice next to these. It’s an easy way to add something fresh to the plate.
Save it for later
This section covers how to store leftovers and what parts of the recipe you can prepare ahead of time.
Storage and Make Ahead
Store the bars airtight at room temperature for up to 3 days. I like to keep them in a single layer if possible so the frosting stays neat. If you need to stack them, use parchment between layers.
For a longer stash, refrigerate them for up to 1 week. The frosting firms up in the fridge, and the bars are actually really good chilled.
You can make them a day ahead with no problem. I usually bake and cool the bars, frost them, then chill until slicing so the edges look clean.
If you want them longer-term, you can freeze individual portions in an airtight container. Thaw in the fridge overnight, or let them sit at room temp until softened a bit.
A few quick answers
This section covers a few extra details that may help before you head to the recipe card.
Recipe FAQs
How do I know when peanut butter bars are done?
I look for lightly golden edges and a center that’s set but still looks soft. If you wait until the middle looks dry, the bars usually end up more cakey and less chewy.
Can I use crunchy peanut butter?
Yes. I like swapping up to half of the creamy peanut butter for crunchy if you want some texture, especially in the bars themselves.
Can I add chocolate chips?
Definitely. Stir about 1 cup of semisweet chocolate chips into the batter, or drizzle melted chocolate over the frosting after it sets a bit.
Why did my frosting turn out too thick or too thin?
If it’s too thick, add milk a tablespoon at a time and beat well between additions. If it’s too thin, beat in a little more powdered sugar until it thickens back up.
Do I have to chill the bars before slicing?
You don’t have to, but it helps a lot. A quick chill (20 to 30 minutes) firms up the frosting so you can cut clean squares without dragging the topping.
You might also like
Before you go, take a look at a few other recipes below the recipe card. They use similar ingredients in a different way and are worth saving too.
MORE DINNER RECIPES TO TRY
Soft and Chewy Old-Fashioned Peanut Butter Bars
INGREDIENTS
Peanut Butter Bars
- 1 cup unsalted butter softened
- 1 cup creamy peanut butter
- 1 cup packed light brown sugar
- ½ cup granulated sugar
- 2 large eggs
- 2 tsp vanilla extract
- 2 cups all purpose flour
- 1 tsp baking soda
- ½ tsp fine salt.
Peanut Butter Frosting
- ½ cup unsalted butter softened
- ½ cup creamy peanut butter
- 2 cups powdered sugar
- 2 to 4 tbsp milk
- 1 tsp vanilla extract
- pinch of salt to taste.
INSTRUCTIONS
Peanut Butter Bars
- Heat oven to 350 F and line a 9 by 13 inch baking pan with parchment leaving overhang and lightly grease
- cream butter peanut butter and both sugars until smooth and fluffy
- beat in eggs and vanilla until combined
- whisk flour baking soda and salt then mix into wet ingredients just until no dry streaks remain
- spread batter evenly in pan and bake until edges are lightly golden and center is set but still soft
- cool completely in pan.
Peanut Butter Frosting
- Beat butter and peanut butter until smooth
- add powdered sugar and beat on low then medium until thick
- beat in vanilla and enough milk to reach a spreadable consistency then add salt to taste
- spread frosting over cooled bars and chill 20 to 30 minutes to set before slicing.
