Peanut Butter Flapjack (Peanut Butter Oat Bars)

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Chewy Peanut butter flapjack with jam is an easy recipe that gives this classic British traybake a nutty twist. They are buttery, oaty, syrupy, jammy and full of peanut flavour.

Try a slice with a peanut butter & jelly milkshake alongside it!

Slices of chewy peanut butter flapjack with a jam centre lined up on a tray.

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Why You'll Love This Recipe

Jammy centre: There's a sticky layer of jam baked into the centre for a fruity bite.

Taste: Buttery, syrupy, nutty and jammy.

Texture: Perfectly chewy.

Quick & Easy: Have this peanut butter and jam flapjack in the oven in around 20 minutes.

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Why You'll Love This Recipe
Ingredients Notes & Substitutions
How to Make Peanut Butter Oat Bars
Storage Instructions
Tips For Perfectly Chewy Flapjack
Expert Tips
Frequently Asked Questions
Variations and Add-ins
Try these easy traybakes too
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Tips For Perfectly Chewy Flapjack
Expert Tips
Variations and Add-ins
💬 Comments

British flapjack (known as oat bars in the U.S.) is a very popular traybake. This flapjack recipe with peanut butter and jam takes inspiration from the popular American sandwich. It's a lovely twist on the classic oat traybake.

For more tasty flapjack recipes try my Biscoff flapjack and cocoa flapjack. They are both deliciously different. Steering in a slightly different direction, take your oats alongside a helping of cornflakes in my popular date bars, cornflake flapjack, or coconut cornflake slices.

Ingredients Notes & Substitutions

Labelled ingredients for a peanut butter flapjack recipe.

Oats: Use regular rolled oats (porridge oats) rather than steel cut oats or jumbo oats. The smaller the oat flakes used the less chance that the flapjack will crumble as they absorb the liquid ingredients fully and they are easier to compress in the tin that larger oats.

Butter: Real butter gives the best flavour to this peanut butter flapjack recipe. Use it if you can. If you need to use dairy-free butter opt for vegan block-style butter and add an extra ¼ teaspoon of salt.

Golden syrup: Sweet, sticky, thick and gorgeously golden, this is a vital ingredient in British flapjack recipes. It's getting easier to find outside of the UK but if you cannot get hold if it the next best alternative would be light corn syrup.

Peanut butter: Use smooth or crunchy, the choice is yours.

Jam/ jelly: The classic American peanut butter and jelly sandwich typically uses grape jelly, which is a smooth, seedless preserve made from Concord grapes. Smuckers and Welch's are popular brands. If you can use this ingredient then do so, but if you cannot get hold of it (or you can only find it at an extortionate price), raspberry jam (preferably seedless) is a great alternative.

How to Make Peanut Butter Oat Bars

Full instructions and measurements are given in the printable recipe card at the end of this post.

Absolutely no fancy skills or equipment are needed to make these peanut butter oat bars.

Butter, brown sugar, golden syrup and peanut butter in a pan.

Step 1: Combine all spices into a large bowl and combine thoroughly with mixture

A person whisking melted ingredients for peanut butter flapjack in a pan.

Step 2: Use a handheld balloon whisk to stir the ingredients until they combine to form a smooth, slightly thick, liquid.

A person stirring oats into liquid ingredients for a flapjack recipe.

Step 3: Add the oats and mix in, using a wooden spoon, until evenly coated.

A layer of jam spread over mixture for flapjack with peanut butter.

Step 4: Spoon approximately half of the oaty mixture into a prepared tin and push down firmly to completely cover the base. spread the jam over the top to within 1cm of the tin edges.

A person pressing peanut butter flapjack mixture into a baking tin using a spoon.

Step 5: Spoon small piles of the remaining oat mixture over the top and carefully spread it out. Use the back of a spoon to press it down gently but firmly to form a level top, covering the jam.

Peanut butter flapjack cut into 12 pieces with the knife alongside.

Step 6: Bake for 25-30 minutes until golden and the edges look a little crispy. The centre will firm up as it cools. After 10 minutes score the top of the flapjack into portions but wait until it is completely cold before cutting it with a sharp knife.

Storage Instructions

Your flapjack with peanut butter and jam should be wrapped in foil and stored in an airtight container at room temperature for up to 5 days.

This peanut butter flapjack can also be frozen. Wrap the bars in food wrap, label and store in the freezer for up to 2 months. Defrost fully, at room temperature, before eating. The texture may be slightly softer than prior to freezing.

Tips For Perfectly Chewy Flapjack

The secret to perfectly chewy flapjack comes down to two things:

Golden syrup: Thick & sticky, it's the perfect ingredient when seeking a chewy texture.
Bake time: I have specified 30 minutes to create flapjack that is chewy in the centre and crisper at the edges. To enhance the chewy texture, cook for slightly less time - try 25 minutes.

Expert Tips

Use the correct sized tin: In this case a 20-cm (8-inch) square tin. If you use a larger tin you will struggle to create a base and cover for the layer of jam in the centre of this flapjack with peanut butter.
Weigh ingredients accurately: The best method is to use digital kitchen scales and measure in grams. I do not give cup measurements because they are wildly inaccurate.
Flatten your flapjack: It's frustrating when your flapjack puffs up around the edges, given it a less professional look. But the fix is easy: as soon as it comes out of the oven run the back of a dessert spoon around the edges of the pan to flatten the flapjack before it cools and sets.

Frequently Asked Questions

Can I make peanut butter flapjack without golden syrup?

Golden syrup is always the best option when making British flapjack. However, if you cannot find it, substitute light corn syrup.

Why is my peanut butter flapjack crumbly?

If you use steel cut or jumbo oats which are larger than rolled oats your flapjack is more likely to fall apart. Similarly, if you did not press the mixture firmly into the tin your peanut butter flapjack is more prone to crumbling. Finally, cutting flapjack whilst hot or warm can leand to breakages.

Why is my flapjack with peanut butter hard and crunchy?

If flapjack is over baked it will turn hard and crunchy once it has cooled.

Can I make vegan flapjack with peanut butter?

Yes, you can. Make sure that you use a vegan block butter substitute and that the sugar used is vegan.

Variations and Add-ins

Add peanuts: Stir 60g of chopped peanuts into the flapjack mixture.
Omit the jam: This will give straightforward chewy peanut butter flapjack recipe.
Chocolate chips: Mix 100g chocolate chips into the oaty mixture. Go for milk chocolate or dark chocolate.
Swap the peanut butter: Try any other nut butter you fancy, such as almond butter, hazelnut butter or pistachio butter.
Drizzle: Warmed peanut butter and/or dark chocolate drizzled across the top of this peanut butter and jam flapjack enhances the presentation.

Slices of flapjack with peanut butter and jam centre lined up side by side..

Try these easy traybakes too

Have you made this easy flapjack recipe with peanut butter and jam? Please leave a rating below as i love to hear how readers get along with my recipes.

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