Easy Peanut Butter Swirl Brownies

Peanut Butter Swirl Brownies with a fudgy brownie base and topped with swirls of sweetened creamy peanut butter. This peanut butter brownie recipe is so easy to make because it starts with a brownie box mix, and a simple 4 ingredient peanut butter swirl batter.

Do you love peanut butter + chocolate as much as I do? You must try these Peanut Butter Bars (better than a Reese’s) and Chocolate Peanut Butter Lush.

Peanut Butter Swirl Brownie Recipe (With A Brownie Mix)

These peanut butter swirl brownies are so easy to make and a quick fix for that chocolate + peanut butter craving! Chocolate and peanut butter is one of the only flavor combos that I crave – and these easy to make brownies are just what I need. 

It starts with a box mix of chocolate fudge brownie mix; prepared to the box directions including the eggs, oil, and water. Spread that into a baking pan and then make the simple 4 ingredient peanut butter mixture that gets swirled on top of the batter. 

I love the look of these pretty brownies with the swirls of peanut butter that create a marbled swirl pattern on top of the chocolate brownies. 

If you prefer more cakey brownies then follow the directions for that on the box (usually you add an extra egg) or try making my Homemade Brownies as the base instead of the boxed mix.

How To Make Peanut Butter Swirl Brownies (Printable Recipe Card)

Preheat the oven to 350 degrees F. Lightly spray a 9×13-inch baking dish or cake pan with nonstick cooking spray. You can also line the baking dish with parchment paper for easier removal. 

Prepare the brownie mix according to directions on the back of the box, using the listed ingredients (eggs, vegetable oil, and water), in a large bowl. Stir all the ingredients together until they are thoroughly combined and no dry pockets remain in the batter, but don’t overmix the brownie batter. 

Place the peanut butter into a microwave-safe heatproof bowl and heat for 30-60 seconds just until it loosens up and becomes smooth and pourable. It should easily flow off a spoon in a thin ribbon. Once it reaches a good consistency, stir in the powdered sugar, vanilla extract, and salt. Mix until the batter thickens slightly but is still soft and easy to spoon. If it firms up too much while mixing, pop it back in the microwave for another 5-10 seconds to loosen it again. 

Pour the brownie batter into the prepared baking dish and smooth the top with a spatula. Use a spoon to drop dollops of the peanut butter batter all over the top of the brownie batter. 

Use a butter knife or a skewer to gently swirl the peanut butter mixture into the brownie batter. Go for a pretty marbled effect/pattern without fully blending it into the brownie batter all the way. 

Bake for 25-35 minutes or until a toothpick inserted into the center comes out with only a few moist crumbs and not wet batter. 

Let the brownies cool completely in the pan on a cooling rack. 

Once the brownies have cooled, cut into squares and enjoy! You can eat the brownies completely cooled to room temperature or eat them slightly warmed (like after they have cooled for at least 30 minutes, otherwise they won’t cut nicely at all). 

How To Store Chocolate Peanut Butter Brownies

Store the brownies in an airtight container, at room temperature, for up to 3 days. They can be eaten at room temperature, or the best way to eat leftovers is to warm up a brownie square in the microwave for 5-10 seconds. 

For extended storage, wrap individual brownies in plastic wrap and then again in aluminum foil. Place the wrapped brownie squares in a freezer-safe Ziploc bag and freeze for up to two months. Let them thaw at room temperature or rewarm gently in the microwave for about 15 seconds. 

Helpful Tips For This Brownie Recipe With Peanut Butter Swirls

1. Warming the peanut butter first makes it super easy to mix it with the powdered sugar and creates a swirl that holds its shape beautifully while baking. 
2. Start checking for doneness around the 20-minute mark. When you insert a toothpick or cake tester into the center, you should see a few moist crumbs clinging to it. You don’t want to see wet batter on the toothpick as that means the brownies need more time to bake through. You also don’t want to overbake the brownies or else they will be dry.
3. I recommend lining the pan with parchment paper. Parchment paper (just like for cookies) helps the brownies bake more evenly and it helps the bottom of the brownies from over browning. I spray the pan first with parchment paper and then press my parchment paper into the pan; the spray helps it adhere and stick better to the pan, so it’s easier to spread the brownie mixture into it. 
4. Drizzle some warmed peanut butter or warmed chocolate chips (semi-sweet or milk) over top the brownies before serving. 
5. Add a handful of peanut butter chips into the brownie batter for more peanut butter goodness. 
6. The brownies can be eaten slightly warmed or at room temperature. If eating warm and gooey, I still recommend letting the brownies cool for at least 20 minutes, that way, they will cut nicely and not fall apart; but still be warm and soft and gooey for serving. 
7. Do not use any peanut butter labeled as ‘all-natural’ or any that has a thick oil layer on top that must be stirred before using. Creamy peanut butter will give you a nice smooth peanut butter swirl, while all-natural peanut butter tends to crack and bake up more dry and dense.

More Must-Try Brownie Recipes

• Easy Snickers Brownies
• 3-Ingredient Nutella Brownies
• Easy Pumpkin Cheesecake Brownies
• Cookies and Cream Brownies
• Chocolate Chip Brownies
• Monster Cookie Brownies
• Candy Bar Brownies
• Andes Mint Cookie Brownies