These oven baked peanut butter cup brownie bars are the kind of shortcut dessert that feels almost too easy for how good it turns out. When a busy week calls for something fun and homemade-ish without pulling out a mixer and a long ingredient list, this recipe delivers with just five simple ingredients and a baking dish. The mini peanut butter cups melt into the brownie base just enough to make every bite extra rich, chewy, and full of that classic chocolate-peanut butter combination everyone reaches for first.
Serve these brownie bars slightly warm with a cold glass of milk, hot coffee, or a scoop of vanilla ice cream if you want to lean into full dessert mode. They also fit right in on a party tray with fresh strawberries, pretzels, or salted mixed nuts to balance the sweetness, and they pack up well for potlucks, bake sales, and family movie nights.
Oven Baked 5-Ingredient Peanut Butter Cup Brownie Bars
Servings: 20 bars
Ingredients
1 box brownie mix, family size for a 9x13-inch pan
2 large eggs
1/2 cup vegetable oil
1/4 cup water
20 to 24 mini peanut butter cups, unwrapped
Directions
1. Preheat your oven to 350°F. Lightly grease a clear glass 9x13-inch baking dish or line it with parchment for easier lifting and slicing.
2. In a large bowl, stir together the brownie mix, eggs, vegetable oil, and water until fully combined. The batter will be thick.
3. Spread about two-thirds of the brownie batter evenly into the prepared baking dish. Scatter the whole unwrapped mini peanut butter cups across the batter in an even layer.
4. Drop the remaining brownie batter over the top in spoonfuls and gently spread it as best you can to partially cover the peanut butter cups. Some candy showing through is perfectly fine.
5. Bake for 30 to 35 minutes, or until the center is set and a toothpick inserted into the brownie portion comes out with moist crumbs but not wet batter.
6. Let the bars cool completely before cutting into squares. For cleaner slices, chill them for 30 minutes after cooling, then cut and serve.
Variations & Tips
Use a different brownie mix: Fudge brownie mix gives the richest, chewiest result, but dark chocolate or milk chocolate brownie mix both work well here. Just make sure the box is sized for a 9x13-inch pan so the layers bake evenly.
Freeze for cleaner cuts: If you want bakery-style squares, cool the pan fully and chill it before slicing. A sharp knife wiped clean between cuts helps keep the peanut butter cups from dragging through the bars.
Add a salty finish: A light sprinkle of flaky sea salt on top right after baking balances the sweetness and makes the chocolate and peanut butter flavors pop a little more.
Try a peanut butter drizzle: Melt a few spoonfuls of peanut butter and drizzle it over the cooled bars for an extra-decadent look. This is a great option when you want them to feel a little more special for a party or holiday tray.