Overnight Egg and Cheese Breakfast Casserole Make Ahead with Turkey Sausage and Veggies
There is something deeply satisfying about waking up knowing breakfast is basically done. This overnight egg and cheese breakfast casserole make ahead recipe is exactly that kind of morning win. You put it together the night before, slide it into the fridge, and then all you have to do in the morning is preheat the oven and pour your coffee. No scrambling, no stress, just a bubbling, golden casserole ready to feed your whole family or a crowd of hungry guests.
What makes this version genuinely healthier than the classic is a combination of smart swaps that actually taste good. Instead of white bread or buttery croissants as the base, we use whole grain sourdough, which brings in more fibre and a subtle tang that plays beautifully against the creamy egg custard. The protein comes from a generous amount of free-range eggs plus lean turkey sausage crumbles, giving each slice around 28 grams of protein. That kind of protein hit in the morning keeps your blood sugar steady and your energy levels up for hours. We also use reduced-fat sharp cheddar, which still melts brilliantly and gives you that full cheesy flavour without the excess saturated fat. A layer of spinach, roasted red peppers, and spring onions adds colour, micronutrients, and an extra gram of fibre per serving without making the dish feel like a salad in disguise.
The overnight rest is not just a convenience trick. It actually makes the casserole better. As the bread soaks in the spiced egg mixture overnight, it absorbs every bit of flavour, so when it bakes, you get a custardy interior with edges that are slightly crisp and deeply golden. We season the egg base with a little smoked paprika, garlic powder, dry mustard, and black pepper, which sounds simple but creates a warmth and depth that makes people ask what your secret ingredient is. The answer, honestly, is just time. Letting those flavours meld overnight does more work than any single herb or spice could on its own.
This casserole is genuinely built for real life. You can prep it on a Sunday evening and have it for meal prep through the week, reheating individual slices in under two minutes. It works just as well for a holiday morning as it does for a regular Tuesday. Cut it into 10 generous squares and each one comes in at around 290 calories, making it a filling breakfast that fits into almost any calorie goal. If you have picky eaters at the table, the variations are endless: swap the turkey sausage for mushrooms and black beans for a vegetarian take, or add a handful of cherry tomatoes and fresh basil for a more Mediterranean feel. However you build it, the overnight egg and cheese breakfast casserole make ahead method is one of those recipes you will come back to again and again.
Ingredients
- 6 thick slices whole grain sourdough bread (cut into 1 inch cubes, about 5 cups)
- 10 large free-range eggs
- 1.5 cups unsweetened almond milk (or low-fat dairy milk)
- 0.5 cup low-fat plain Greek yogurt (adds creaminess without heavy cream)
- 340 g lean turkey sausage (casings removed, crumbled and cooked through)
- 1.5 cups reduced-fat sharp cheddar cheese (grated, divided)
- 2 cups fresh baby spinach (roughly chopped)
- 1 cup roasted red peppers (from a jar, drained and roughly chopped)
- 4 stalks spring onions (thinly sliced, white and green parts)
- 2 cloves garlic (finely minced)
- 1 tsp smoked paprika
- 0.5 tsp dry mustard powder
- 0.5 tsp garlic powder
- 0.5 tsp fine sea salt
- 0.3 tsp black pepper (freshly ground)
- 1 tsp olive oil (for greasing the dish)
Instructions
- 1
Lightly grease a 9x13 inch baking dish with olive oil. Spread the cubed whole grain sourdough bread evenly across the bottom of the dish in a single loose layer.
Day-old or slightly stale bread works best here. It absorbs the egg mixture more evenly without going soggy.
- 2
In a large skillet over medium heat, cook the crumbled turkey sausage for 6 to 8 minutes, breaking it up as it cooks, until browned all the way through. Add the minced garlic and cook for another 30 seconds until fragrant. Remove from heat.
Drain any excess liquid from the pan before adding the sausage to the casserole.
- 3
Scatter the cooked turkey sausage over the bread cubes. Then layer on the chopped spinach, roasted red peppers, and sliced spring onions. Sprinkle 1 cup of the grated cheddar evenly over the top.
- 4
In a large mixing bowl, whisk together the eggs, almond milk, Greek yogurt, smoked paprika, dry mustard, garlic powder, sea salt, and black pepper until completely smooth and well combined.
Whisking the Greek yogurt in thoroughly prevents any lumps and makes the custard extra silky.
- 5
Pour the egg mixture slowly and evenly over all the ingredients in the baking dish. Gently press down on the bread cubes with the back of a spatula so they start to soak up the liquid. Sprinkle the remaining 0.5 cup of cheddar over the top.
- 6
Cover the baking dish tightly with plastic wrap or a fitted lid and refrigerate for at least 8 hours or overnight. This soaking time is essential for the best texture.
You can refrigerate for up to 18 hours if you want to prep further in advance.
- 7
When you are ready to bake, remove the casserole from the fridge and let it sit on the counter for 20 minutes while the oven preheats to 190 degrees Celsius or 375 degrees Fahrenheit.
Bringing the dish closer to room temperature helps it bake more evenly and reduces the risk of a still-cold centre.
- 8
Remove the cover and bake uncovered for 45 to 50 minutes, until the top is golden brown, the edges are set, and the centre no longer jiggles when you gently shake the dish.
If the top starts to brown too quickly around the 35-minute mark, loosely tent with foil for the remaining bake time.
- 9
Remove from the oven and let the casserole rest for 10 minutes before slicing into 10 squares and serving.
Resting allows the custard to firm up slightly, making the slices much cleaner and easier to lift out.
Nutrition per serving
290kcal
Calories
28g
Protein
18g
Carbs
11g
Fat
3g
Fibre
3g
Sugar
480mg
Sodium
Pro Tips
- ✓
Use a mix of whole eggs and egg whites if you want to reduce the fat further while keeping the protein high.
- ✓
Do not skip the resting period after baking. It makes a real difference to how cleanly the casserole slices.
- ✓
Grating your own cheddar from a block melts far more smoothly than pre-shredded bags, which contain anti-caking agents.
- ✓
If you are baking it fresh without the overnight rest, use slightly drier or toasted bread and bake for an extra 5 minutes.
- ✓
Covering the dish tightly overnight stops the egg custard from developing a skin and keeps everything fresh.
Frequently Asked Questions
Variations
- •
Vegetarian Black Bean Version
Skip the turkey sausage and add one 400g can of drained black beans plus 1 cup of sliced mushrooms sauteed in a little olive oil with garlic. This keeps the protein up while making the dish fully plant-friendly.
- •
Mediterranean Style
Replace the turkey sausage with 1 cup of sun-dried tomatoes and a handful of pitted kalamata olives. Use crumbled reduced-fat feta instead of cheddar, and add a teaspoon of dried oregano and a pinch of chilli flakes to the egg mixture.
- •
Spicy Southwest
Add half a teaspoon of chipotle powder and a teaspoon of cumin to the egg mixture. Stir in half a cup of drained black beans and half a cup of corn kernels with the vegetables. Top with a small handful of pickled jalapenos before baking and serve with a dollop of low-fat plain yogurt.
- •
Dairy-Free Version
Use unsweetened oat milk instead of almond milk, replace the Greek yogurt with a thick coconut yogurt, and swap the cheddar for a melting-style dairy-free cheese. The texture stays creamy and the casserole still sets beautifully.
Substitutions
- •Whole grain sourdough bread → Gluten-free bread or courgette slices (Use slightly stale gluten-free bread for the best absorption. Courgette slices make a great low-carb base.)
- •Turkey sausage → Chicken sausage or black beans (Chicken sausage works as a direct swap. Black beans add plant-based protein for a vegetarian version.)
- •Almond milk → Low-fat dairy milk or oat milk (Any unsweetened milk alternative works here. Oat milk gives a slightly creamier result.)
- •Greek yogurt → Low-fat sour cream or silken tofu blended smooth (Sour cream gives a tangier flavour. Silken tofu is a great dairy-free option that keeps the custard silky.)
- •Reduced-fat cheddar → Gruyere, mozzarella, or dairy-free cheddar (Gruyere adds a nuttier depth of flavour. Mozzarella melts very smoothly and keeps the calories lower.)
- •Baby spinach → Kale or finely chopped Swiss chard (Massage kale briefly before using to soften it slightly so it integrates better into the casserole.)
🧊 Storage
Once baked, cool the casserole to room temperature and cover the dish tightly with plastic wrap or foil. Store in the refrigerator for up to 4 days. Reheat individual slices in the microwave for 1 to 2 minutes, or cover the whole dish with foil and reheat in the oven at 175 degrees Celsius for 15 to 20 minutes until warmed through. For freezing, slice into portions and freeze in airtight containers or wrapped individually for up to 2 months.
📅 Make Ahead
This recipe is designed to be made ahead. Assemble the full casserole the night before, cover tightly and refrigerate for 8 to 18 hours. In the morning, take it out of the fridge 20 minutes before baking, then bake uncovered at 190 degrees Celsius for 45 to 50 minutes. You can also fully bake it ahead of time and simply reheat slices as needed throughout the week for quick weekday breakfasts.
