Overnight Blueberry French Toast Casserole with Streusel Topping

A pan of cubed bread left overnight in custard absorbs it on an entirely different timeline than a quick dip ever could. Every corner of every cube gets saturated evenly, all the way through, so nothing comes out of the oven dry or under-soaked the way a rushed morning version sometimes does.

That overnight wait is what makes this one worth planning ahead for. The blueberries burst slightly as it bakes, and the streusel on top turns deeply golden and crisp against the soft custard underneath.

Why You Will Love This Recipe

• An overnight soak means the bread absorbs custard fully and evenly, all the way to the center.
• The oven does the work for a whole tray at once, no standing at the stove flipping individual pieces.
• A crisp streusel topping adds crunch and sweetness without any extra effort in the morning.
• Bursting blueberries throughout mean juicy pockets of fruit in every serving.
• Perfect for feeding a crowd at brunch with almost no morning-of prep required.

Ingredients

• 8 cups cubed day-old brioche or challah bread
• 1 1/2 cups fresh or frozen blueberries
• 4 large eggs
• 2 cups whole milk
• 1/2 cup heavy cream
• 1/2 cup granulated sugar
• 1 tablespoon vanilla extract
• 1 teaspoon ground cinnamon
• 1 teaspoon lemon zest
• 1/2 cup all-purpose flour, for the streusel
• 1/3 cup brown sugar, for the streusel
• 1/2 teaspoon ground cinnamon, for the streusel
• 6 tablespoons cold unsalted butter, cubed, for the streusel
• Warm maple syrup, for serving

Crockery and Time To Create

• 1 9×13 inch ceramic or glass baking dish
• 1 large mixing bowl
• 1 medium mixing bowl
• 1 whisk
• 1 pastry cutter or fork
• Prep time: 20 minutes (plus overnight chill)
• Cook time: 45 minutes
• Total time: 1 hour 5 minutes (plus overnight chill)
• Servings: 8

Ingredient Substitutions and Variations

• French bread or sourdough: replaces brioche for a slightly less rich, chewier texture.
• Frozen blueberries: replace fresh, no need to thaw first, just toss directly into the layers.
• Half-and-half: replaces heavy cream for a slightly lighter custard.
• Almond milk: replaces whole milk for a dairy-light version with a nearly identical texture.
• Rolled oats: fold a quarter cup into the streusel for extra texture and heartiness.
• Orange zest: replaces lemon zest for a warmer, slightly sweeter citrus note.
• Cream cheese cubes: dot a few pieces throughout the layers for pockets of tangy richness.

Step-by-Step Instructions

Whisk the Custard

In the large mixing bowl, whisk together the eggs, milk, heavy cream, granulated sugar, vanilla extract, cinnamon, and lemon zest until fully combined and smooth, about 1 minute.

Layer the Bread and Blueberries

Spread half of the cubed bread evenly in the baking dish, scatter half of the blueberries over the top, then repeat with the remaining bread and blueberries in a second layer.

Pour the Custard Over the Layers

Pour the custard slowly and evenly over the bread and blueberries, gently pressing down with a spatula so every cube absorbs some of the liquid.

Chill Overnight

Cover the dish tightly and refrigerate for at least 8 hours or overnight, allowing the bread to fully absorb the custard.

Make the Streusel Topping

In the medium mixing bowl, combine the flour, brown sugar, and cinnamon, then cut in the cold butter with the pastry cutter until the mixture forms coarse, pea-sized crumbs.

Sprinkle the Streusel Over the Casserole

Remove the casserole from the refrigerator and sprinkle the streusel evenly over the entire top surface just before baking.

Bake Until Golden

Bake in a preheated 350 degree Fahrenheit oven for 40 to 45 minutes, until the top is deeply golden and the center feels set when gently pressed.

Rest and Serve

Let the casserole rest for 5 minutes before serving warm with a generous drizzle of maple syrup.

Pro Tips for Best Results

• Use slightly stale bread if possible, since fresh bread turns mushy after a full overnight soak.
• Press the bread down gently after pouring the custard so every piece gets fully saturated.
• Do not skip the overnight chill, since it is what allows the custard to soak all the way through.
• Add the streusel right before baking rather than the night before, so it stays crisp instead of soggy.
• Tent loosely with foil if the top browns too quickly before the center finishes baking.

Common Mistakes to Avoid

• Using very fresh, soft bread: this turns mushy overnight, always use slightly stale or day-old bread.
• Skipping the overnight chill: the center stays wet and undercooked without enough soak time, always chill fully.
• Adding the streusel too early: it can turn soggy if left on overnight, always add it just before baking.
• Underbaking: a jiggly center means it needs more time, bake until the middle feels set when pressed.

What to Serve With

• Crispy turkey sausage links: a savory, protein-rich pairing that balances the sweetness of the casserole.
• Fresh berries on the side: adds brightness and a juicy contrast to the rich baked custard.
• A pot of hot coffee: a classic brunch pairing that rounds out the meal for a crowd.

Storage and Reheating

• Refrigerator: store cooled leftovers covered for up to 4 days.
• Freezer: freeze individual portions in an airtight container for up to 1 month.
• Reheating: warm in a 300 degree Fahrenheit oven for 10 minutes, or microwave individual portions for 30 seconds.

Nutrition Information

Nutrient	Per Serving
Calories	390 kcal
Protein	9 g
Carbohydrates	48 g
Sugars	24 g
Fat	18 g
Saturated Fat	10 g
Sodium	280 mg
Nutrition values are estimates only and will vary based on specific ingredients and brands used.

Health Benefits

Blueberries are naturally high in antioxidants and fiber, adding real nutritional value to a dish that might otherwise be considered purely indulgent.

Baking instead of pan-frying individual slices means no added butter for repeated batches, keeping the overall fat content more contained across the whole tray.

Conclusion

This is the breakfast to make the night before a big morning, so all that is left to do is slide it into the oven. Give this casserole a try for your next brunch gathering, and if it becomes a go-to for busy mornings, save the recipe and pass it along to anyone who always ends up rushing breakfast for a crowd.