Overnight Baked French Toast Casserole with Brioche and Vanilla Protein Custard

Name: Overnight Baked French Toast Casserole with Brioche and Vanilla Protein Custard
Prep time: 20 min
Cook time: 45 min
Total time: 9 h 5 min
Yield: 8 servings
Ingredients: 400 g brioche bread (cut or torn into roughly 2cm chunks, slightly stale works best); 4 large eggs; 240 ml unsweetened almond milk (or any unsweetened non-dairy milk); 200 g plain low-fat Greek yogurt (adds creaminess and protein); 3 tbsp pure maple syrup (plus extra for serving if desired); 1.5 tsp pure vanilla extract; 1.5 tsp ground cinnamon (divided); 0.25 tsp ground nutmeg; 0.25 tsp fine sea salt; 150 g fresh strawberries (hulled and sliced); 100 g fresh blueberries; 60 g rolled oats (old-fashioned oats, not instant); 1.5 tbsp coconut oil (melted and slightly cooled); 1 tbsp raw honey (drizzled over the oat topping before baking); 1 tsp coconut sugar (for the oat topping); 1 pinch sea salt (for the oat topping)

High ProteinMeal Prep

Prep Time20 min

Cook Time45 min

Servings8

Calories285 kcal

Health Score5/10

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Overnight Baked French Toast Casserole with Brioche and Vanilla Protein Custard

There is something genuinely magical about waking up knowing breakfast is already done. This overnight baked French toast casserole with brioche gives you exactly that. You spend about fifteen minutes in the kitchen the night before, slide the dish into the fridge, and by morning all you have to do is turn on the oven. The result is a golden, custardy bake that smells like a bakery and tastes completely indulgent, yet it is built on a foundation of wholesome ingredients that actually fuel your body rather than crash it.

Most traditional French toast casseroles lean hard on heavy cream, loads of refined sugar, and very little protein. This version takes a different approach without sacrificing any of the comfort you are after. The custard is made with a blend of whole eggs, unsweetened almond milk, and plain Greek yogurt. The yogurt does two things brilliantly. It adds a gentle tang that makes the flavour more complex, and it bumps the protein content significantly so each serving keeps you full well past mid-morning. A modest amount of pure maple syrup sweetens the mixture naturally, and a touch of raw honey on top during baking creates that caramelised, slightly crisp top layer that everyone fights over.

Brioche is still the star of the show here, and rightly so. Its light, buttery crumb soaks up custard better than almost any other bread. To keep things a little more balanced, this recipe uses a slightly smaller quantity of brioche than most versions and adds a layer of sliced fresh strawberries and blueberries tucked between the bread chunks. The berries soften beautifully overnight, releasing natural juices that weave through the custard and add fibre, antioxidants, and a fresh brightness that cuts through the richness. The cinnamon and vanilla in the custard tie everything together into one cohesive, warming flavour.

For the topping, skip the traditional butter-and-sugar streusel and use a simple mix of rolled oats, a small amount of coconut oil, cinnamon, and a pinch of sea salt. It bakes into a crunchy, nutty crumble that adds satisfying texture and a little extra fibre without the sugar spike. This casserole is ideal for holiday mornings, weekend brunches, or any time you want to feed a group something genuinely delicious without standing at the stove. Serve it warm with a drizzle of extra maple syrup if you like, or keep it simple with a spoonful of Greek yogurt on the side. Either way, it disappears fast.

Ingredients

Serves:8

400 g brioche bread (cut or torn into roughly 2cm chunks, slightly stale works best)
4 large eggs
240 ml unsweetened almond milk (or any unsweetened non-dairy milk)
200 g plain low-fat Greek yogurt (adds creaminess and protein)
3 tbsp pure maple syrup (plus extra for serving if desired)
1.5 tsp pure vanilla extract
1.5 tsp ground cinnamon (divided)
0.3 tsp ground nutmeg
0.3 tsp fine sea salt
150 g fresh strawberries (hulled and sliced)
100 g fresh blueberries
60 g rolled oats (old-fashioned oats, not instant)
1.5 tbsp coconut oil (melted and slightly cooled)
1 tbsp raw honey (drizzled over the oat topping before baking)
1 tsp coconut sugar (for the oat topping)
1 pinch sea salt (for the oat topping)

Instructions

1
Lightly grease a 9x13 inch baking dish with a little coconut oil or cooking spray. Arrange half the brioche chunks in an even layer across the bottom of the dish.
Day-old or slightly dried-out brioche absorbs the custard more evenly and holds its shape better. If your bread is very fresh, spread the chunks on a baking sheet and leave them out for an hour or two.
2
Scatter the sliced strawberries and blueberries evenly over the first layer of bread. Top with the remaining brioche chunks, pressing down very gently so everything is somewhat compact.
Frozen berries can work in a pinch. Thaw them first and pat them dry to prevent too much liquid pooling at the base.
3
In a large mixing bowl, whisk together the eggs, almond milk, Greek yogurt, maple syrup, vanilla extract, 1 teaspoon of the cinnamon, nutmeg, and fine sea salt until the mixture is smooth and the yogurt is fully incorporated with no lumps.
Whisking the yogurt in thoroughly is important. Any large lumps will create uneven custard pockets in the finished casserole.
4
Pour the custard mixture slowly and evenly over the bread and berries, making sure every piece of bread gets coated. Use the back of a spoon or your hands to press the bread down gently into the liquid so it starts absorbing.
5
Cover the dish tightly with cling film or a fitted lid and refrigerate for at least 6 hours, or overnight for best results. The bread should absorb most of the custard during this time.
Eight hours is the sweet spot. The longer soak means a more uniform, custardy texture all the way through with no dry patches.
6
When you are ready to bake, preheat your oven to 175 degrees Celsius (350 degrees Fahrenheit). While the oven heats, make the oat topping by combining the rolled oats, melted coconut oil, coconut sugar, remaining half teaspoon of cinnamon, and pinch of sea salt in a small bowl. Mix until the oats are well coated.
7
Remove the casserole from the fridge and let it sit at room temperature for about 10 minutes while the oven finishes preheating. Sprinkle the oat topping evenly over the surface, then drizzle the raw honey all over the top.
Letting the dish sit briefly at room temperature helps it bake more evenly from edge to centre.
8
Bake uncovered for 40 to 45 minutes until the top is golden brown and the oat crumble is crisp. The centre should be set with just a very slight jiggle. A knife inserted into the middle should come out with moist but not liquid custard.
If the top browns too quickly before the centre is set, lay a sheet of foil loosely over the dish for the last 10 minutes of baking.
9
Remove from the oven and let the casserole rest for 5 minutes before slicing and serving. Serve warm with an extra drizzle of maple syrup or a spoonful of Greek yogurt on the side.

Nutrition per serving

285kcal

Calories

13g

Protein

34g

Carbs

10g

Fat

Fibre

12g

Sugar

230mg

Sodium

Pro Tips

✓
Slightly stale brioche absorbs the custard beautifully without turning mushy. If your loaf is very fresh, cube it and leave it uncovered on the counter for a couple of hours before assembling.
✓
Do not skip the overnight rest. Six to eight hours of soaking transforms the texture completely, giving you that soft, custardy interior that makes this casserole so satisfying.
✓
The oat topping is best added just before baking, not the night before, so it stays crunchy and does not absorb moisture from the fridge.
✓
For extra protein, stir a scoop of unflavoured or vanilla protein powder directly into the custard mixture before pouring it over the bread.
✓
Room temperature eggs whisk more smoothly into the custard than cold eggs straight from the fridge.

Frequently Asked Questions

Can I make this overnight baked French toast casserole with brioche the night before?↓

Absolutely, and that is actually the best way to make it. Assembling the casserole the evening before and letting it soak overnight gives the brioche time to fully absorb the custard. In the morning you just add the oat topping and bake. It is genuinely one of the easiest make-ahead breakfasts you can have on rotation.

How do I know when the casserole is fully cooked?↓

Look for a deep golden colour on top and a crumble that has crisped up. Insert a knife or skewer into the very centre of the dish. It should come out with moist custard clinging to it but no wet, runny liquid. The edges will be slightly firmer than the middle, and that is completely normal.

Can I use a different bread instead of brioche?↓

Brioche gives the best results because its enriched dough absorbs custard without falling apart, but you can use a good-quality whole grain challah or sourdough if you prefer a slightly denser, higher-fibre result. Avoid sliced sandwich bread as it tends to turn too soft and loses structure.

Is this recipe suitable for meal prep?↓

It is great for meal prep. Bake the casserole, let it cool completely, then slice it into individual portions and refrigerate for up to four days. Reheat single portions in the microwave for about 90 seconds or warm them in the oven at 160 degrees Celsius for 10 minutes. The texture holds up very well.

How can I make this dairy-free?↓

The almond milk is already dairy-free. Swap the Greek yogurt for an unsweetened coconut or soy yogurt with a similar thick consistency. The custard will be slightly less tangy but still works well. The overall texture stays custardy and delicious.

Variations

•
Apple Cinnamon Version
Replace the berries with one large peeled and diced apple tossed in a little cinnamon and lemon juice. Add a quarter teaspoon of ground cardamom to the custard for a warming autumn flavour. The apple softens beautifully overnight and pairs wonderfully with the oat crumble topping.
•
Banana Nut Version
Layer two sliced ripe bananas between the brioche chunks instead of berries. Add two tablespoons of natural almond butter whisked into the custard for richness and extra protein. Scatter a handful of chopped walnuts over the top along with the oat crumble before baking.
•
Pumpkin Spice Version
Whisk three tablespoons of pure pumpkin puree and half a teaspoon of pumpkin spice blend into the custard mixture. Skip the berries and fold in a small handful of dried cranberries tucked between the bread layers. This version is especially good in autumn and around the holiday season.

Substitutions

•
Unsweetened almond milk → Oat milk or unsweetened soy milk (Both provide a similar creamy result. Soy milk adds a small amount of extra protein. Oat milk gives a slightly sweeter, more neutral flavour.)
•
Plain low-fat Greek yogurt → Coconut yogurt or soy yogurt (Use a thick, unsweetened variety to maintain the custard consistency. Protein content will be slightly lower with coconut yogurt.)
•
Pure maple syrup → Raw honey or date syrup (Both work as a one-for-one swap. Date syrup adds extra fibre and a deeper caramel-like sweetness. Reduce quantity slightly if using honey as it is sweeter.)
•
Coconut oil → Light olive oil or avocado oil (Either works well in the oat topping. Olive oil gives a more neutral flavour. Avocado oil has a very mild taste and a high smoke point.)
•
Brioche bread → Whole grain challah or sourdough (Whole grain options add fibre and have a slightly denser crumb. Soak time may need to increase by 30 minutes to allow full custard absorption.)

🧊 Storage

Cool the casserole completely before covering. Store leftovers in the baking dish covered tightly with cling film, or transfer individual slices to an airtight container. Refrigerate for up to 4 days. Reheat individual portions in the microwave for 60 to 90 seconds or in an oven preheated to 160 degrees Celsius for 8 to 10 minutes. The oat topping loses some crunch after refrigerating but regains it slightly when oven-reheated.

📅 Make Ahead

Assemble the casserole up to the end of step 4 the night before, cover tightly, and refrigerate for 6 to 8 hours. The oat crumble topping should be made fresh on the morning of baking and scattered over the top just before it goes into the oven. Do not add it the night before or it will absorb moisture and lose its texture.