Protein Flapjacks: UK Bars Compared and an Easy Recipe

A protein flapjack is an oat flapjack with whey, soy or pea protein added, which lifts it from the 5 to 7g of protein per 100g in an ordinary flapjack to anywhere between 15 and 25g. UK bars run from 40g snacks with about 160 calories and 10g of protein to 120g bars like Phoenix Bars, with up to 557 calories and 19g of protein in one bar. You can also make them at home with oats, nut butter, syrup and protein powder, and the recipe is below.

Written by James Frost, founder of Flaming Phoenix and the maker of Phoenix Bars. Updated 2 November 2026.

Why I wrote this. Phoenix Bars are flapjacks with added soy and pea protein, so I spend a lot of time reading other protein flapjack labels. This guide compares the main UK bars on their published labels, including where my own bars fit, and shows you how to make a batch at home.

What is a protein flapjack?

It is a British flapjack, oats bound with fat and syrup, with a protein ingredient added to the mix. Brands use whey or milk protein, soy protein crispies or pea protein, and some add a chocolate or yoghurt-style coating. The oats still do most of the work: they supply the carbohydrate, the chew and much of the fibre, while the added protein roughly triples what you would get from a plain bar.

That makes a protein flapjack a different thing from most protein bars. A protein bar is usually built around the protein, while a protein flapjack is still an oat bar first, with plenty of carbohydrate alongside. For the plain version, see my guide to flapjack bars.

How much protein is in a protein flapjack?

Between 9 and 20g per bar on the bars compared below, which works out at roughly 15 to 25g per 100g. An ordinary flapjack has 5 to 7g per 100g, all from the oats. Bigger bars carry more protein in total, so check the per-bar figure on the label rather than the per-100g column.

Protein contributes to the maintenance of muscle mass, which is why people training hard or trying to put weight on look for it. If you want a number to aim for, my protein calculator for weight gain works out a daily target from your body weight.

UK protein flapjacks compared

Figures come from each brand’s published label or a major UK retailer listing, checked in November 2026, and are per bar. Recipes change and flavours vary a little, so check the pack you buy. They are listed from the most calories per bar to the fewest.

1. Phoenix Bars: the most calories and protein in one bar

• 120g bar: 529 to 557 calories, 18 to 19g of protein and 60 to 66g of carbohydrate, depending on flavour.
• Pressed oat flapjack made with coconut oil and added soy and pea protein, in six flavours.
• Keeps for up to two years (12 months for Cherry Bakewell) and will not freeze or melt.
• Eat it as a bar, break it into pieces over a few hours, or mix it with water or milk into porridge.
• £5.25 a bar, made in the UK.

I make Phoenix Bars, so weigh my view accordingly. They are built for days when you need a lot of calories without a lot of food: long hikes and ultras, a missed meal, or getting more calories in when your appetite is small. They are sold as high calorie protein bars, and customers call them flapjacks too: 42 of 391 published reviews use the word.

Allergen note: Phoenix Bars contain soy, the Cherry Bakewell flavour contains almonds, and some flavours contain sulphites. The label carries a “may contain” warning for milk, egg, nuts, peanuts and sesame.

2. Muscle Moose Big Protein Flapjack

• 100g bar: about 443 to 456 calories and 15g of protein, depending on flavour.
• Oat flapjack with added protein from a Stockport brand; the golden syrup version contains milk.
• Sold online and in some shops.

The closest thing to a meal-sized flapjack among the sports brands, with a little less protein per bar than the smaller bars below.

3. Myprotein Protein Flapjack

• 80g bar: about 324 to 342 calories and 20g of protein, depending on flavour.
• Baked oat flapjack with added protein; suitable for vegetarians and contains milk.
• Sold online by Myprotein, usually in boxes of 12.

The most protein per bar on this list, in a soft, baked bar that sits between a snack and a small meal.

4. Precision Engineered Protein Flapjack

• 75g bar: about 239 calories and 18g of protein.
• Sold by Holland and Barrett and described as low in sugar.

A lot of protein for the calories, so it suits someone watching their total intake more than someone trying to eat more.

5. Trek Protein Flapjack

• 50g bar: about 217 to 244 calories and 9 to 10g of protein, depending on flavour.
• Made with gluten-free oats and soy protein crispies, and suitable for vegans.
• Sold in most big supermarkets, singly or in multipacks.

The easiest one to pick up on the way somewhere, and a good size for a snack.

6. Oatein Flapjack

• 40g bar: about 160 calories and 10g of protein. Oatein also makes a larger 75g bar with about 18g.
• Oven-baked in the UK.

The smallest bar here, with a lot of protein for its size.

Which protein flapjack should you buy?

• For the most calories and protein in one bar: Phoenix Bars, up to 557 calories and 19g of protein in only 120g.
• For the most protein per bar: Myprotein, at 20g.
• For the most protein per calorie: Precision Engineered or Oatein.
• For a supermarket snack: Trek.
• For putting weight on or a small appetite: one big bar does more than several small ones, which is why people choose high calorie bars for weight gain. My best energy bars for weight gain guide covers the wider field.
• For hiking and long runs: pick a firm bar that survives a rucksack and can be eaten in pieces. My guides to the best energy bars for hiking and the best energy bars for ultra running go further.

How to make protein flapjacks

This makes 12 bars in a 20cm square tin. The figures are worked from typical UK labels, so treat the totals as close estimates.

Ingredients

• 250g porridge oats
• 60g protein powder (about two scoops of whey, or a vegan pea or soy powder)
• 100g smooth peanut butter
• 120g runny honey or golden syrup
• 70g butter or baking block (or 60g coconut oil for a dairy-free version)
• A pinch of salt

Method

1. Heat the oven to 170C (150C fan, gas mark 3) and line the tin with baking paper.
2. Melt the butter, peanut butter and honey together over a low heat, stirring until smooth, then take the pan off the heat.
3. Mix the oats, protein powder and salt in a large bowl, pour in the melted mixture and stir until every oat is coated. If it looks dry and crumbly, add a tablespoon or two of milk or water.
4. Press firmly into the tin, packing it down hard with the back of a spoon.
5. Bake for 15 to 18 minutes, until just golden at the edges. Protein powder dries out faster than plain oats, so take it out a little earlier than a normal flapjack.
6. Score into 12 while warm, leave to cool completely in the tin, then cut.

Per bar: about 225 calories and 8g of protein. Cut the tin into 8 instead and each bar is about 335 calories and 12g of protein.

Tips

• Unflavoured or vanilla protein powder works best; chocolate powder gives a brownie-style bar.
• For gluten-free bars, use oats labelled gluten free and check your protein powder. My gluten free flapjacks guide covers the swaps.
• For vegan bars, use a pea or soy protein, coconut oil and golden or maple syrup, as in my vegan flapjacks.
• For a bigger, more filling bar, my high-calorie flapjack recipe adds nuts and chocolate.
• Keep them in an airtight tin for up to a week, or wrap and freeze for up to three months.

What customers say

Marc R. used Phoenix Bars on a 42-mile fast pack across the Brecon Beacons and called them “great tasting flapjacks with a high amount of carbs”. A customer who powerlifts, and whose appetite does not match her training, wrote that they “make it easy to add more calories and protein without adding a significantly greater volume of food”. Another, training for a 170km race, enjoyed “mixing them with water to make a nutritious porridge for breakfast”.

Frequently asked questions

Are protein flapjacks healthy?

They are a convenient way to get oats, carbohydrate and protein in one snack, but most still contain plenty of sugar and fat, as any flapjack does. Whether one suits you depends on what you need: someone trying to eat more will value the calories, while someone eating less may prefer a smaller bar. Compare the per-bar figures on the label.

Are protein flapjacks good for weight gain?

They can help, because a bigger bar adds calories and protein without a lot of extra food. A 120g Phoenix Bar adds up to 557 calories in one go. My guide on how to gain weight shows how many extra calories a day to aim for.

How many calories are in a protein flapjack?

From about 160 calories for a 40g bar to 529 to 557 calories for a 120g Phoenix Bar. Most sit between 220 and 350 calories, and the homemade bars above are about 225 calories each.

Can you eat a protein flapjack before or during exercise?

Yes, if it agrees with you. The oats give you carbohydrate for long efforts, and a firm bar can be broken into pieces and eaten over a few hours. Try it in training before you rely on it in a race.

Are protein flapjacks vegan or gluten free?

Some are. Trek and Phoenix Bars are vegan and made with gluten-free oats, while several others, including Myprotein and the golden syrup Muscle Moose bar, contain milk. Always check the allergen statement on the pack.

How long do protein flapjacks keep?

Homemade bars keep for about a week in an airtight tin. Shop-bought bars carry a best before date on the pack, and Phoenix Bars keep for up to two years from production (12 months for Cherry Bakewell).

Related guides

• Porridge bars: recipe and UK buys
• Homemade high calorie bars
• Best high calorie foods for bulking
• How to use Phoenix Bars
• High calorie bars from Flaming Phoenix

Sources: brand and retailer labels for Muscle Moose, Myprotein, Precision Engineered, Trek and Oatein, checked November 2026; ingredient figures from typical UK supermarket labels.