Name: Overnight Blueberry French Toast Casserole - A Make-Ahead Breakfast Favorite
Prep time: 15 min
Cook time: 45 min
Total time: 60 min
Ingredients: 1 loaf (14 to 16 ounces) day-old brioche or challah, cut into 1-inch cubes; 2 cups fresh or frozen blueberries (no need to thaw if frozen); 8 large eggs; 2 1/2 cups whole milk or 1 1/2 cups milk + 1 cup half-and-half for extra richness; 1/2 cup granulated sugar; 1/4 cup brown sugar, packed; 2 teaspoons pure vanilla extract; 1 teaspoon ground cinnamon; 1/4 teaspoon ground nutmeg (optional); 1/2 teaspoon fine sea salt; 2 tablespoons unsalted butter, melted, plus more for greasing the dish; 2 tablespoons turbinado sugar (optional, for a crisp top); Maple syrup, for serving; Powdered sugar, for serving; Lemon zest from 1 lemon (optional, brightens the blueberry flavor)

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This Overnight Blueberry French Toast Casserole is the kind of breakfast that makes mornings feel easy and special. You put it together the night before, let the bread soak up the custard, and bake it fresh in the morning. The result is soft, fluffy French toast with pockets of juicy blueberries and a golden, lightly crisp top.

It feels cozy and homemade, yet it’s simple enough for any weekend. Whether you are feeding a crowd or just want leftovers for the week, this casserole won’t let you down.

What Makes This Recipe So Good

Make-ahead convenience: Assemble at night, bake in the morning. No morning mess or fuss.
Perfect texture: The bread soaks overnight, so you get a creamy center and a slightly crisp top.
Balanced sweetness: Not too sugary on its own, leaving room for maple syrup or a dusting of powdered sugar.
Blueberries in every bite: Fresh or frozen berries burst with flavor and color.
Reliable and flexible: Works with different bread types, dairy options, and toppings.

Ingredients

1 loaf (14 to 16 ounces) day-old brioche or challah, cut into 1-inch cubes
2 cups fresh or frozen blueberries (no need to thaw if frozen)
8 large eggs
2 1/2 cups whole milk or 1 1/2 cups milk + 1 cup half-and-half for extra richness
1/2 cup granulated sugar
1/4 cup brown sugar, packed
2 teaspoons pure vanilla extract
1 teaspoon ground cinnamon
1/4 teaspoon ground nutmeg (optional)
1/2 teaspoon fine sea salt
2 tablespoons unsalted butter, melted, plus more for greasing the dish
2 tablespoons turbinado sugar (optional, for a crisp top)
Maple syrup, for serving
Powdered sugar, for serving
Lemon zest from 1 lemon (optional, brightens the blueberry flavor)

Step-by-Step Instructions

Prep the dish: Grease a 9×13 inch baking dish with butter. Set aside.
Cube the bread: Cut the brioche or challah into 1-inch cubes. If the bread is very fresh, spread the cubes on a sheet pan and let them sit out for 30 to 60 minutes to dry a bit.
Layer the casserole: Add half the bread cubes to the dish. Scatter half the blueberries over the bread.
Top with the remaining bread and then the remaining blueberries.
Make the custard: In a large bowl, whisk together eggs, milk, granulated sugar, brown sugar, vanilla, cinnamon, nutmeg, salt, melted butter, and lemon zest if using. Whisk until smooth and well combined.
Soak the bread: Pour the custard evenly over the bread and berries, pressing gently with the back of a spatula so the top layer starts to absorb the liquid. Cover tightly with foil or wrap.
Chill overnight: Refrigerate for at least 6 hours and up to 18 hours.
The longer soak helps the center become custardy and tender.
Preheat and prep: In the morning, take the dish out of the fridge while you preheat the oven to 350°F. Let the casserole sit at room temperature for 20 minutes to remove the chill.
Add a crunchy top: If you like a crisp finish, sprinkle turbinado sugar evenly over the surface.
Bake: Cover with foil and bake for 25 minutes. Remove the foil and bake another 20 to 25 minutes, until the top is golden and the center is set with only a slight jiggle.
An instant-read thermometer in the center should read about 175°F to 185°F.
Rest and serve: Let it rest for 10 minutes. Dust with powdered sugar, slice into squares, and serve with warm maple syrup.

Keeping It Fresh

Refrigerate leftovers in an airtight container for 3 to 4 days. Reheat individual portions in the microwave for 45 to 60 seconds, or bake covered at 325°F for 10 to 15 minutes until warm.

Freeze for later by wrapping cooled slices tightly in plastic, then in foil, and storing in a freezer bag for up to 2 months.

Thaw overnight in the fridge and reheat in the oven at 325°F until heated through.

Avoid sogginess by placing reheated pieces on a baking sheet so the bottoms stay a bit crisp instead of steaming.

Health Benefits

Blueberries: Rich in antioxidants like anthocyanins that support heart and brain health.
Eggs: Provide high-quality protein, B vitamins, and choline for energy and focus.
Milk: Adds calcium and vitamin D for bones. You can use reduced-fat milk to lower calories.
Portion control: Because it is filling, a modest square goes a long way and helps prevent over-snacking later.
Balanced approach: Pair with a side of Greek yogurt or a fresh fruit salad to round out the meal.

Pitfalls to Watch Out For

Using very fresh bread: Fresh bread can turn mushy. Day-old or lightly dried bread holds texture better.
Skipping the chill time: If the bread does not soak, the center can be dry while the top gets too brown.
Overbaking: Too long in the oven causes a dry, rubbery custard.
Check for a slight jiggle or use a thermometer.
Not seasoning enough: Salt and vanilla matter. They enhance sweetness and bring out the blueberry flavor.
Uneven layering: If the berries clump in one spot, you will have dry corners and soggy pockets. Scatter them evenly.

Recipe Variations

Lemon almond: Add 1 teaspoon almond extract and extra lemon zest.
Top with sliced almonds before baking.
Cream cheese swirl: Dot the layers with small cubes of softened cream cheese for a tangy, cheesecake-like vibe.
Streusel top: Mix 1/2 cup flour, 1/2 cup brown sugar, 1 teaspoon cinnamon, and 4 tablespoons cold butter until crumbly. Sprinkle on top before baking.
Dairy-free: Use full-fat coconut milk or almond milk and a plant-based butter. Choose a sturdy vegan bread if needed.
Whole grain: Swap half the brioche with whole wheat bread.
Increase vanilla and cinnamon slightly to balance flavor.
Mixed berries: Replace half the blueberries with raspberries or blackberries for extra color and tartness.

FAQs

Can I use frozen blueberries?

Yes. Use them straight from the freezer. Do not thaw, or they will bleed more color into the custard.

Add 5 minutes to the bake time if needed.

What is the best bread for this casserole?

Brioche and challah are ideal because they are rich and sturdy. Texas toast or a rustic French loaf also work if you slightly dry the cubes first.

How do I know when it is done?

The top should be golden and the center should have a slight jiggle. A thermometer reading in the center should be around 175°F to 185°F.

If it looks pale, give it a few more minutes uncovered.

Can I make this without refined sugar?

You can swap the granulated and brown sugar for 1/2 cup maple syrup or honey. Reduce the milk by 2 to 3 tablespoons to keep the custard from getting too thin.

What if I do not have time to chill overnight?

Let it soak for at least 30 to 45 minutes at room temperature. It will not be as custardy, but it will still bake up nicely.

How can I keep the top from getting too dark?

Tent the dish with foil for the first half of baking.

Remove the foil for the final 20 to 25 minutes to brown the top evenly.

Can I add protein?

Absolutely. Serve with turkey sausage, bacon, or Greek yogurt on the side. You can also fold in 1 cup of chopped toasted nuts for extra crunch and staying power.

Final Thoughts

This Overnight Blueberry French Toast Casserole brings together ease, comfort, and bright berry flavor in one dish.

With simple prep the night before, your morning becomes stress-free and delicious. It is a crowd-pleaser for holidays, brunches, or a treat-yourself weekend. Keep the basics in mind, adjust to your taste, and enjoy a warm slice with maple syrup on top.