Vegetarian High-Protein Caprese Egg White Frittata

After years of trying to stretch my weekly food budget without sacrificing my protein goals, I landed on this Vegetarian High-Protein Caprese Egg White Frittata. It uses simple, affordable ingredients like carton egg whites and fresh mozzarella, bakes into a fluffy, sliceable meal, and costs just over £1.50 per serving — perfect for batch cooking on a Sunday.

Recipe Overview

• Prep Time: 10 minutes
• Cook Time: 25 minutes
• Total Time: 35 minutes (plus 5 minutes resting)
• Servings: 6 generous slices
• Difficulty: Easy — suitable for beginners

Why You’ll Love This Vegetarian High-Protein Caprese Egg White Frittata

• Budget-friendly meal prep: At roughly £1.50 per serving, this frittata costs less than a shop-bought sandwich and provides double the protein.
• Over 25g of protein per slice: Thanks to a full carton of egg whites and low-fat mozzarella, each serving packs a serious protein punch to keep you full until your next meal.
• Batch cooks beautifully: I’ve been making this for over 9 years, and it never disappoints. It keeps in the fridge for up to five days and freezes brilliantly for those weeks when you need a quick, grab-and-go breakfast or lunch.
• No fancy equipment required: You only need one ovenproof skillet or a small baking dish — no steamers, no blenders, no complicated gadgets.
• Endlessly adaptable: Swap the mozzarella for feta or cheddar, add wilted spinach or roasted peppers, or turn up the heat with chilli flakes. The base recipe is forgiving and welcomes whatever you have on hand.

Vegetarian High-Protein Caprese Egg White Frittata

15 min prep  ·  30 min cook  ·  4 servings

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Ingredients You’ll Need

• 1 tablespoon olive oil
• 1 small onion, finely diced (about 100g)
• 2 cloves garlic, minced
• 750ml (about 3 cups) liquid egg whites from a carton
• 200g cherry tomatoes, halved
• 150g fresh mozzarella, torn into small pieces
• 60g grated Parmesan cheese
• 2 tablespoons fresh basil, roughly chopped, plus extra for garnish
• 1 teaspoon dried oregano
• ½ teaspoon fine sea salt
• ¼ teaspoon freshly ground black pepper
• Butter or non-stick spray for greasing the pan

Tip: For the most budget-friendly version, buy a large carton of liquid egg whites from a supermarket rather than separating whole eggs. It’s significantly cheaper per gram of protein and reduces waste. If you prefer, you can use 12 large egg whites from fresh eggs instead.

How to Make Vegetarian High-Protein Caprese Egg White Frittata

1. Preheat your oven to 180°C (350°F) and position a rack in the middle. Grease a 23cm (9-inch) ovenproof non-stick skillet or a similar-sized baking dish with butter or spray. The pan should feel slick but not greasy to the touch.
2. Sauté the aromatics: Heat the olive oil in the skillet over medium heat. Add the diced onion and cook for 4-5 minutes, stirring occasionally, until the pieces turn translucent and the edges just begin to brown. The kitchen should smell sweet and savoury. Stir in the minced garlic and cook for 30 seconds — you’ll know it’s ready when the garlic becomes fragrant but hasn’t coloured.
3. Whisk the egg whites: In a large bowl, pour in the liquid egg whites. Add the dried oregano, salt, and pepper. Whisk vigorously for about 30 seconds until the mixture is uniformly pale yellow and slightly frothy on top. You should see small bubbles forming across the surface — that’s air being incorporated, which helps the frittata rise.
4. Assemble in the pan: Spread the cooked onion and garlic evenly across the bottom of the skillet. Arrange the halved cherry tomatoes cut-side up, nestling them into the onion layer. Scatter the torn mozzarella pieces and half the Parmesan evenly over the top. Slowly pour the whisked egg whites over everything, tilting the pan gently so the liquid settles into all the gaps. The tomatoes and cheese should be partially submerged but still visible.
5. Bake the frittata: Place the skillet in the preheated oven and bake for 20-25 minutes. After 15 minutes, check the frittata — the edges should be set and pulling away slightly from the pan, while the centre still jiggles when you gently shake the skillet. Sprinkle the remaining Parmesan over the top and continue baking. The frittata is done when the centre is just set and a knife inserted into the middle comes out clean, with no wet egg clinging to it. The top should be puffed and golden in patches, and you’ll hear a faint sizzle as the cheese bubbles.
6. Rest and garnish: Remove the skillet from the oven and place it on a wire rack. Let the frittata rest for 5 full minutes — this is crucial for the texture (see tips below). The surface will settle slightly as it cools. Scatter the fresh basil over the top and slice into 6 wedges. The slices should hold their shape cleanly without crumbling.

Tips From My Kitchen

• Don’t skip the onion sauté: Cooking the onion first removes its raw, pungent bite and develops natural sweetness. If you add raw onion directly to the egg whites, it will release water during baking and make the frittata soggy. The golden-brown colour on the onion tells you the sugars have caramelised, which adds depth to the final dish.
• Let the egg whites come to room temperature: Cold egg whites straight from the fridge will take longer to cook, leading to an uneven texture where the outside is overdone and the centre is still runny. Take the carton out of the fridge 15-20 minutes before you start cooking. If you’re short on time, place the sealed carton in a bowl of lukewarm water for 5 minutes.
• Use a metal or ceramic pan, not glass: Glass baking dishes retain heat differently and can cause the frittata to stick or cook unevenly. A well-seasoned cast-iron skillet or a non-stick ovenproof pan gives the best results — the sides conduct heat evenly, and the frittata releases easily after resting.
• Resist the urge to overbake: Egg whites continue to cook from residual heat after you remove the frittata from the oven. If you wait until the centre is completely firm, the edges will be rubbery and dry. Pull it out when the centre still has a slight wobble — it will set perfectly during the 5-minute rest.
• Portion before storing: For meal prep, slice the frittata into individual wedges while it’s still slightly warm. This prevents the slices from sticking together in the container and makes it easy to grab one portion at a time. Wrap each wedge tightly in baking paper or place them in a single layer in an airtight container.
• Freeze for up to 3 months: After testing this recipe five times, I finally got it just right for freezing. Let the sliced frittata cool completely, then wrap each piece individually in cling film and place them in a freezer bag. To reheat, thaw overnight in the fridge and warm in a microwave for 60-90 seconds, or pop the frozen slice directly into a 160°C oven for 12-15 minutes.

Common Mistakes to Avoid

• Overcrowding the pan: If you add too many tomatoes or too much cheese, the frittata becomes heavy and releases excess liquid during baking. Stick to the quantities listed — the egg whites need room to puff up and set. If you want to add extra vegetables like spinach or mushrooms, sauté them first to remove moisture, then reduce the tomato quantity slightly.
• Wrong temperature: Baking at too high a temperature (above 190°C) will cause the frittata to puff dramatically and then collapse, leaving a dense, rubbery texture. Too low (under 160°C) and it will take too long to set, drying out the edges. The sweet spot is 180°C — it’s hot enough to create a light, airy structure but gentle enough to cook evenly through.
• Skipping the rest time: The 5-minute rest isn’t optional — it allows the proteins in the egg whites to relax and reabsorb any steam trapped inside. Cutting into the frittata immediately will release that steam and leave you with a wet, deflated slice. Resting also makes the slices firmer and cleaner to cut, which is essential for meal prep presentation.

Delicious Variations to Try

• Spicy Version: Add ½ teaspoon of red chilli flakes to the egg whites before whisking, and swap the cherry tomatoes for 100g of roasted red peppers from a jar. For extra heat, scatter a few thin slices of fresh red chilli over the top before baking.
• Vegetarian/Vegan Option: Replace the egg whites with 600ml of firm silken tofu blended until smooth, and use a plant-based mozzarella alternative. Add 1 tablespoon of nutritional yeast to the tofu mixture for a cheesy flavour. The texture will be denser but still satisfying, and the protein content remains high.
• Different Protein: For a non-vegetarian twist, fold 150g of shredded cooked chicken or thinly sliced turkey breast into the egg whites before pouring them into the pan. This works beautifully if you have leftover meat from a High Protein Ground Turkey Chili — simply shred the turkey and scatter it over the onion layer.

What to Serve With Vegetarian High-Protein Caprese Egg White Frittata

• A crisp green salad with a simple lemon vinaigrette — the acidity cuts through the richness of the cheese.
• Toasted sourdough or a wholemeal wrap for extra carbohydrates if you’re serving this as a main meal.
• Roasted cherry tomatoes on the vine alongside, drizzled with balsamic glaze for a double hit of tomato flavour.
• A dollop of Cottage Cheese Ranch Dip With Veggies on the side adds creaminess and an extra 5g of protein per serving.

Frequently Asked Questions

Vegetarian High-Protein Caprese Egg White Frittata

A light and fluffy egg white frittata packed with cherry tomatoes, fresh mozzarella, and Parmesan, inspired by classic Caprese flavors. Perfect for a high-protein, low-carb breakfast or main course.

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Prep Time 15 minutes mins

Cook Time 30 minutes mins

Total Time 45 minutes mins

Servings: 4 servings

Course: Main Course

Cuisine: American

Calories: 350

Ingredients Method Notes

Ingredients

  

• 1 tablespoon olive oil
• 1 small onion finely diced (about 100g)
• 2 cloves garlic minced
• 750 ml about 3 cups liquid egg whites from a carton
• 200 g cherry tomatoes halved
• 150 g fresh mozzarella torn into small pieces
• 60 g grated Parmesan cheese
• 2 tablespoons fresh basil roughly chopped, plus extra for garnish
• 1 teaspoon dried oregano
• ½ teaspoon fine sea salt
• ¼ teaspoon freshly ground black pepper
• Butter or non-stick spray for greasing the pan

Method

 

1. Preheat your oven to 180°C (350°F) and position a rack in the middle. Grease a 23cm (9-inch) ovenproof non-stick skillet or a similar-sized baking dish with butter or spray. The pan should feel slick but not greasy to the touch.
2. Sauté the aromatics: Heat the olive oil in the skillet over medium heat. Add the diced onion and cook for 4-5 minutes, stirring occasionally, until the pieces turn translucent and the edges just begin to brown. The kitchen should smell sweet and savoury. Stir in the minced garlic and cook for 30 seconds — you'll know it's ready when the garlic becomes fragrant but hasn't coloured.
3. Whisk the egg whites: In a large bowl, pour in the liquid egg whites. Add the dried oregano, salt, and pepper. Whisk vigorously for about 30 seconds until the mixture is uniformly pale yellow and slightly frothy on top. You should see small bubbles forming across the surface — that's air being incorporated, which helps the frittata rise.
4. Assemble in the pan: Spread the cooked onion and garlic evenly across the bottom of the skillet. Arrange the halved cherry tomatoes cut-side up, nestling them into the onion layer. Scatter the torn mozzarella pieces and half the Parmesan evenly over the top. Slowly pour the whisked egg whites over everything, tilting the pan gently so the liquid settles into all the gaps. The tomatoes and cheese should be partially submerged but still visible.
5. Bake the frittata: Place the skillet in the preheated oven and bake for 20-25 minutes. After 15 minutes, check the frittata — the edges should be set and pulling away slightly from the pan, while the centre still jiggles when you gently shake the skillet. Sprinkle the remaining Parmesan over the top and continue baking. The frittata is done when the centre is just set and a knife inserted into the middle comes out clean, with no wet egg clinging to it. The top should be puffed and golden in patches, and you'll hear a faint sizzle as the cheese bubbles.
6. Rest and garnish: Remove the skillet from the oven and place it on a wire rack. Let the frittata rest for 5 full minutes — this is crucial for the texture (see tips below). The surface will settle slightly as it cools. Scatter the fresh basil over the top and slice into 6 wedges. The slices should hold their shape cleanly without crumbling.

Notes

Letting the frittata rest for 5 minutes after baking is crucial for a clean slice and optimal texture. For best results, use a well-seasoned non-stick skillet.

I’d love to hear how you get on with this Vegetarian High-Protein Caprese Egg White Frittata. Have you tried it with different cheeses or added your favourite vegetables? Drop a comment below and share your meal prep wins — I read every single one. If you’re looking for another protein-packed meal to batch cook, my High Protein Teriyaki Chicken Meal Prep Bowls are a fantastic companion recipe for the week ahead.