Name: High Protein Sweet Potato Casserole
Prep time: 20 min
Cook time: 60 min
Total time: 100 min
Ingredients: 450 g zucchini (grated, plus salt for drawing out moisture); 250 g sweet potato (peeled into thin ribbons); 120 g yellow onion (thinly sliced into rings); ½ teaspoon avocado oil (plus extra for spraying); 650 ml egg whites; 2 large eggs; 150 g non-fat Greek yoghurt; 30 g Parmesan Reggiano cheese (grated); 1 teaspoon Dijon mustard; 1 teaspoon garlic powder; Salt and black pepper (to taste)

Jump to Recipe - Print Recipe

This one started as a fridge-clean-out recipe and turned into something I make on purpose now. It’s roasted sweet potato and zucchini folded into an egg bake with Greek yoghurt and Parmesan high in protein, low in fuss, and just as good cold from the fridge two days later as it is warm out of the oven.

No fancy technique here. Grate the zucchini, roast the sweet potato so it actually caramelizes instead of going soft and pale, whisk up the egg mixture, and bake. The only step that actually matters is squeezing the moisture out of the zucchini skip that and you’ll end up with a watery centre.

slice of high protein sweet potato casserole egg bake

Why You’ll Love This High Protein Casserole

It’s built almost entirely from eggs, egg whites, and Greek yoghurt, so you get a genuinely high protein serving without any protein powder involved. The sweet potato and zucchini add fibre and keep it from feeling like “diet food” it just tastes like a good bake.

It’s also easy to make ahead. Bake it the night before and you’ve got breakfast, lunch, or a light dinner sorted for a few days. It reheats well and holds together enough to eat with your hands if you’re in a rush.

And it looks better than the effort it takes the sweet potato ribbons on top caramelize into something that looks deliberate, even though it’s just leftovers from the roasting tray.

Simple Ingredients

Zucchini: Grate it and salt it first to draw out the moisture. Skip this and the bake turns watery in the middle it’s the one step that actually matters.

Sweet potato: Peel it into thin ribbons and roast separately so it caramelizes instead of steaming inside the egg mixture. Half goes into the bake, half sits on top.

Yellow onion: Thin rings, roasted alongside the sweet potato. Roasting takes the sharpness off it.

Avocado oil: Just enough to help everything roast and crisp at the edges without adding much flavour of its own.

Egg whites and whole eggs: Mostly egg whites for volume and protein, a couple of whole eggs for richness so it doesn’t taste flat.

Non-fat Greek yoghurt: Makes the crumb softer and adds more protein without adding fat.

Parmesan Reggiano: A small amount, but it does a lot of the flavour work.

Dijon mustard and garlic powder: Round out the egg mixture so it isn’t bland, without taking over.

Recipe Details

Servings: 6
Preparation time: 20 minutes
Roasting time: 15–20 minutes
Bake time: 50–60 minutes
Total time: Approximately 1 hour 40 minutes

Recommended Equipment

Box grater
Vegetable peeler
Large mixing bowl
Baking sheet
Parchment paper
8 x 8-inch baking dish
Clean kitchen towel (for squeezing moisture from the zucchini)
Whisk

What You’ll Need

450 g zucchini, grated, plus salt for drawing out moisture
250 g sweet potato, peeled into thin ribbons
120 g yellow onion, thinly sliced into rings
½ teaspoon avocado oil, plus extra for spraying
650 ml egg whites
2 large eggs
150 g non-fat Greek yoghurt
30 g Parmesan Reggiano cheese, grated
1 teaspoon Dijon mustard
1 teaspoon garlic powder
Salt and black pepper, to taste

How to Make a High Protein Sweet Potato & Zucchini Bake

Salt the Zucchini: Toss the grated zucchini with a generous pinch of salt in a colander or bowl, then let it sit for at least 5 minutes. This draws out the excess moisture that would otherwise leave your bake watery in the centre.

Roast the Sweet Potato and Onion: Spread the sweet potato ribbons and onion rings across a parchment-lined baking sheet in a single layer. Spray lightly with avocado oil and season with a pinch of salt. Roast at 400°F (200°C) for 15–20 minutes, until the edges are turning golden and slightly caramelized.

Make the Egg Mixture: While the vegetables roast, whisk together the egg whites, whole eggs, Greek yoghurt, Parmesan, Dijon mustard, garlic powder, and a good pinch of pepper until smooth and well combined.

Prepare the Zucchini: Once the sweet potato is out of the oven, reduce the temperature to 350°F (175°C). Squeeze the salted zucchini firmly in a clean kitchen towel to remove as much liquid as possible this step matters more than it looks like it should.

Assemble: Set aside a few of the prettiest roasted sweet potato ribbons for the top. Fold the squeezed zucchini, the remaining sweet potato ribbons, and the roasted onion into the egg mixture until evenly distributed.

Bake: Pour the mixture into a parchment-lined 8 x 8-inch baking dish. Arrange the reserved sweet potato ribbons decoratively across the top. Bake at 350°F (175°C) for 50–60 minutes, until the centre is set, a knife inserted comes out clean, and the top is lightly golden.

Rest and Serve: Let the bake rest for 10 minutes before slicing this keeps it from crumbling and lets the centre finish setting. Slice into squares and serve warm, or let it cool completely for meal prep.

What to Serve With It

A simple green salad with lemon vinaigrette
Roasted asparagus or green beans
A dollop of extra Greek yoghurt and fresh herbs on top
Sliced avocado on the side
Hot sauce or chilli flakes if you want more kick

Nutritional Information

Approximate values per serving (6 servings), based on the ingredients as listed. These are estimates and will vary depending on the specific brands used.

Calories: 180
Protein: 20g
Fat: 5g
Carbohydrates: 13g

Top Tips

Don’t skip squeezing the zucchini. It’s the single step that determines whether your bake sets cleanly or turns watery in the middle. Take the extra minute with the towel.

Roast the sweet potato separately first. Folding it in raw would leave it undercooked and pale; roasting it first is what gives the finished bake its caramelized flavour and colour.

Use a good non-stick or parchment-lined dish. The egg base is delicate enough that a well-lined pan makes turning out slices far easier.

Let it rest before slicing. Ten minutes off the heat lets the centre finish setting, so you get clean squares instead of a crumbly mess.

Make it ahead. This bake keeps beautifully in the fridge and reheats without drying out, which makes it one of the easier make-ahead breakfasts or lunches to have on hand.

High Protein Sweet Potato Casserole – Recipe Variations

Add greens: Fold a handful of chopped spinach or kale in with the zucchini for extra colour and nutrients.

Make it dairy-free: Swap the Parmesan for a dairy-free alternative and use a plain dairy-free yoghurt in place of the Greek yoghurt.

Spice it up: A pinch of smoked paprika or chilli flakes in the egg mixture adds warmth without overwhelming the dish.

Individual portions: Divide the mixture into a muffin tin instead of a baking dish for grab-and-go portions reduce the bake time to around 20–25 minutes.

Rice cooker version: If you’d rather make this hands-off, the egg mixture and roasted vegetables can be layered into a rice cooker insert and cooked on the porridge or slow-cook setting until set a nice companion to our one pot rice cooker meals collection.

More High Protein Recipes You’ll Love

If you liked this one, try my Spanakopita frittata another rice-cooker-friendly egg bake with spinach, feta, and garlic. Or if you want something even faster, my crispy air fryer salmon bites is a five-minute high protein option for the same kind of week.