Peanut Butter Protein Banana Brownies (Bake Recipe)

These peanut butter banana brownies bake in an 8 × 8-inch pan at 350°F (177°C), with ripe bananas, eggs, cocoa, oat flour, and protein powder. Mix the batter just until combined, then bake until the center reaches 160°F (71°C). Cool for at least 20 minutes before cutting for brownies that are moist, set, and easier to lift from the pan.

When a brownie craving meets a bowl of ripe bananas on the counter, this recipe gives both a useful purpose. It also offers a change from the usual banana bread or protein shake. The batter comes together in one bowl, and the oven does the cooking while you get on with dinner or the rest of your evening.

I focus on a few details that matter in a protein-rich bake: measure the ingredients, avoid overmixing, and check the center rather than relying only on the timer. Those steps help you get a tender brownie without leaving the middle underdone or baking it until dry.

Recipe at a glance

This recipe makes one 8 × 8-inch pan of banana brownies. Ripe bananas provide moisture and sweetness, while peanut butter, eggs, protein powder, cocoa, and oat flour build the batter. Use the measurements below as written for the most predictable texture.

Sweetened protein powder can make the brownies overly sweet, so unsweetened powder gives you more control. Protein powders differ in flavor and how much moisture they absorb. The recipe is designed around a measured 40 g, but the exact texture may vary by brand.

Material Setup & Pan Preparation

Pan material affects how quickly heat moves into the batter and how long the brownies keep baking after leaving the oven. A light-colored aluminum pan is the most predictable choice here. Whatever you use, check its manufacturer’s oven limit and let hot bakeware cool gradually.

Use an oven-rated 8 × 8-inch (20 × 20 cm) pan. Light-colored aluminum heats evenly for this bake and makes the 20–25-minute timing a useful guide. Stainless steel is generally nonreactive with this near-neutral batter as well.

Glass and ceramic heat more slowly and retain heat longer than aluminum. Your brownies may need longer in the oven, but carryover baking also continues after you take the pan out. Start checking early and use the center temperature and surface cues, not aluminum’s timing, to decide when they are done.

Avoid bare copper, unlined reactive metal, and poorly seasoned reactive cookware. Always follow the maker’s stated oven-temperature limit, especially for coated pans, pans with handles, and ceramic bakeware; there is no single safe maximum for every product. Induction compatibility does not matter for a recipe baked in the oven.

Heat the oven to 350°F (177°C). If your bake times often vary, check the oven’s actual temperature with an oven thermometer. Line the pan with parchment, leaving enough overhang on two sides to lift out the cooled brownies. Lightly grease the parchment if it shifts or sticks. There is no need to preheat the empty pan.

Culinary Technique & Baking Execution

The batter needs little handling: mash, whisk, stir, and bake. Mix the wet ingredients first, then add the dry ingredients and stop as soon as no dry pockets remain. This approach helps avoid a dense, tough result and makes the recipe easy to follow in a single bowl.

1. Mash the bananas. In a medium bowl, mash the peeled bananas until mostly smooth. A few small soft pieces are fine.
2. Add the wet ingredients. Whisk in the peanut butter and eggs until the mixture looks evenly combined. If the peanut butter is firm, stir it well before measuring.
3. Add the dry ingredients. Stir in the protein powder, cocoa, oat flour, baking powder, and salt. Mix just until no dry patches remain. Fold in chocolate chips, if using.
4. Fill the pan. Scrape the batter into the lined pan and spread it into an even layer. A level surface helps it bake at a similar rate across the pan.
5. Bake and check. Bake for 20 minutes, then check the center. Continue for a few minutes if needed, checking again before 25 minutes. Glass or ceramic may need a different bake time.
6. Cool and release. Remove the pan when the surface is set and the center has reached the safe temperature described below. Let the brownies cool in the pan for at least 20 minutes, then lift them out using the parchment.

The timer is a guide, not a doneness test. Because this batter contains eggs, insert a clean food thermometer into the center, taking care not to touch the pan. The center should reach at least 160°F (71°C). A set surface is another useful cue, but it does not replace the temperature check.

Protein-rich batters can dry out if they stay in the oven too long. Once the center has reached the target and the surface is set, remove the pan promptly. Cooling helps the brownies finish setting, so avoid cutting while they are hot.

Doneness and Texture Troubleshooting

Doneness means the center has reached a safe temperature and the brownies have set enough to hold their shape. Texture depends in part on your pan, oven, banana size, and protein powder. Use the checks below to adjust your next step without guessing from appearance alone.

If your oven seems to run hot or cool, an oven thermometer can help explain why the same timer gives different results. Also check that the pan sits level in the oven and that the batter is spread evenly. For the next batch, change one factor at a time so you can tell what improved the result.

Cleaning, Care & Critical Failure Risk

The main pan-care risk is a sudden temperature change, especially with glass or ceramic. Let the pan cool on a dry, heat-safe surface before washing it. Use mild cleaning tools that suit the pan’s surface, and follow the manufacturer’s care directions for coated or specialty bakeware.

Do not pour cold water onto hot glass or ceramic. Rapid temperature changes can cause thermal shock, which may crack the pan. Sudden changes can also damage some coated bakeware, so let any pan cool gradually before cleaning.

Once the pan is cool, remove the parchment and crumbs. Wash with warm water and mild detergent, then dry fully. For nonstick or ceramic-coated surfaces, avoid steel wool, abrasive scouring powders, and metal utensils, which can scratch or wear the coating. Avoid aerosol cooking sprays on nonstick coatings; their residue can be difficult to remove.

Seasoning care does not apply to intact nonstick, glass, ceramic, or aluminum pans. If you use seasoned cast iron or carbon steel, avoid prolonged soaking and dry the pan immediately to protect its seasoning.

Serving & Dining Presentation

Cooling makes the brownies easier to lift and slice cleanly. After at least 20 minutes in the pan, use the parchment overhang to transfer them to a cutting board. Wipe the knife between cuts for tidier edges, and serve plain or with a little yogurt or sliced banana.

Store leftovers in a covered container in the refrigerator and use within 3–4 days. If you prefer a softer bite, let a portion sit briefly at room temperature before serving. Keep the rest covered and chilled.

For a simple batch, leave out the chocolate chips. For a more chocolate-forward version, include the optional 30 g. Keep the rest of the ingredient amounts the same so the batter’s balance remains close to the tested formula.

Frequently asked questions

Can I use sweetened protein powder?
Yes, but it may make the brownies overly sweet. Unsweetened protein powder is the better choice if you want more control over sweetness.

What size pan should I use?
Use an oven-rated 8 × 8-inch (20 × 20 cm) pan. A different size changes the batter’s depth and may change the bake time.

How long do I bake the brownies?
Start checking at 20 minutes. In a light-colored aluminum pan, the usual window is 20–25 minutes, but confirm doneness in the center rather than relying on time alone.

What temperature should the center reach?
For this egg-containing batter, the center should reach at least 160°F (71°C). Use a clean thermometer probe and avoid touching the pan.

Can I bake them in a glass or ceramic dish?
Yes, if the dish is rated for oven use and you follow its manufacturer’s limits. Glass and ceramic heat more slowly and retain heat longer, so do not rely on the aluminum bake time.

Why are my brownies dry?
They may have baked too long or been mixed more than needed. Check the center early, remove the pan once the center reaches 160°F (71°C) and the surface is set, and stir only until the dry ingredients disappear.

Do I need to preheat the pan?
No. Heat the oven to 350°F (177°C), but put the batter into a room-temperature, lined pan.

How long should they cool before cutting?
Cool them in the pan for at least 20 minutes before lifting them out. More cooling can make the pieces easier to handle.

How should I store leftovers?
Keep them in a covered container in the refrigerator and use them within 3–4 days.

Can I wash the pan while it is hot?
Wait until it cools to room temperature. Do not expose hot glass or ceramic to cold water, since a sudden temperature change can crack it.

(This article was written by one of our staff writers, Steven R. Bancroft. Visit our Meet the Team page.)