Overnight Christmas Strata With Spinach, Peppers, and Gruyère

Why You’ll Love This Recipe

• Perfect make-ahead Christmas morning breakfast: all the work is done the night before.
• Cozy flavors from Gruyère, spinach, and roasted red peppers in every bite.
• Feeds a crowd easily, with simple, affordable ingredients.
• Customizable: add cooked sausage, bacon, or mushrooms if your family loves meat.

Grocery List

• Produce: 1 small yellow onion, 3 garlic cloves, 8 oz baby spinach, fresh thyme (optional)
• Dairy: 1 lb Gruyère cheese, Parmesan cheese (optional), 10 large eggs, whole milk, heavy cream, butter
• Pantry: 1 lb crusty French or Italian bread, jarred roasted red peppers, olive oil, Dijon mustard, kosher salt, black pepper, ground nutmeg

Full Ingredients

For the Strata

• 1 lb crusty French or Italian bread, preferably a day old, cut into 1-inch cubes (about 10 cups lightly packed)
• 1 Tbsp unsalted butter, softened, for greasing the baking dish
• 2 Tbsp olive oil, divided (for sautéing)
• 1 small yellow onion, finely diced (about 1 cup)
• 3 cloves garlic, minced
• 8 oz fresh baby spinach (about 8 packed cups)
• 1/2 tsp kosher salt, for seasoning vegetables
• 1 cup jarred roasted red peppers (about 8 oz), drained, patted dry, and sliced into thin strips
• 8 oz Gruyère cheese, shredded (about 2 packed cups)
• 2 oz Parmesan cheese, finely grated (about 1/2 cup, optional but recommended for a golden top)

For the Egg Custard

• 10 large eggs
• 2 1/2 cups whole milk
• 1 cup heavy cream
• 1 1/2 tsp kosher salt
• 1 tsp Dijon mustard
• 1/2 tsp freshly ground black pepper
• 1/4 tsp ground nutmeg
• 1 tsp fresh thyme leaves, chopped, or 1/2 tsp dried thyme (optional but delicious)

For Finishing

• 2 Tbsp unsalted butter, melted (or olive oil), for drizzling on top before baking
• Extra fresh thyme leaves or chopped parsley, for garnish (optional)

Step-by-Step Instructions

Step 1: Prep the pan and dry out the bread

Grease a 9×13-inch (3-quart) baking dish with the 1 tablespoon of softened butter, making sure to coat the corners and sides well so the strata does not stick.

Spread the bread cubes in a single layer on one or two baking sheets. Place them in a 350°F (175°C) oven for 10–12 minutes, stirring once halfway through, until they are dry to the touch and just starting to feel crisp around the edges but not browned. This helps the bread soak up the custard without turning mushy. Let the bread cool slightly while you prepare the filling.

Step 2: Sauté the onions, garlic, and spinach

In a large skillet, heat 2 tablespoons of olive oil over medium heat. Add the diced onion and 1/2 teaspoon kosher salt. Cook, stirring occasionally, until the onion is soft and translucent, 5–7 minutes.

Add the minced garlic and cook for 30 seconds, just until fragrant. Pile in the baby spinach (it will look like a lot at first). Cook, stirring frequently, until the spinach is completely wilted and any excess liquid has evaporated, 3–5 minutes. If the pan looks watery, continue cooking until it is mostly dry; this prevents the strata from becoming soggy. Remove from heat and set aside to cool slightly.

Step 3: Layer the bread, spinach, peppers, and cheese

Spread half of the toasted bread cubes evenly in the prepared baking dish. Top with half of the spinach mixture, distributing it evenly over the bread. Scatter half of the sliced roasted red peppers over the spinach.

Sprinkle half of the shredded Gruyère and half of the Parmesan (if using) over the vegetables. Repeat with the remaining bread, spinach mixture, roasted red peppers, and cheeses to create a second layer. Try to get some cheese all the way to the edges, as it will brown beautifully in the oven.

Step 4: Whisk together the egg custard

In a large mixing bowl, crack in the 10 eggs and whisk until the yolks and whites are fully combined. Add the whole milk, heavy cream, 1 1/2 teaspoons kosher salt, Dijon mustard, black pepper, nutmeg, and thyme (if using). Whisk until the mixture is smooth and everything is well incorporated. The Dijon and nutmeg give the strata subtle depth without overpowering the other flavors.

Step 5: Combine and chill overnight

Slowly pour the egg custard evenly over the layered bread and vegetables, moving the bowl around the pan so every part is moistened. Use the back of a spoon or clean hands to gently press the bread down into the liquid so that most of it is submerged. Some pieces may stick up slightly; that is fine and will create a lovely crisp top.

Cover the baking dish tightly with plastic wrap or foil. Refrigerate for at least 8 hours and up to 24 hours. During this time, the bread will fully absorb the custard, giving you a rich, sliceable strata with great texture.

Step 6: Bake until puffed and golden

When you are ready to bake, remove the strata from the refrigerator and let it sit at room temperature for about 20–30 minutes while you preheat the oven. This helps it cook more evenly.

Preheat the oven to 350°F (175°C). Uncover the strata and drizzle the top evenly with the 2 tablespoons of melted butter (or olive oil). Place the dish on the middle rack and bake for 45–55 minutes, until the top is deeply golden, the edges are bubbling, and the center is just set. A knife inserted near the center should come out mostly clean with no runny egg. If the top is browning too quickly before the middle is set, loosely tent with foil for the last 10–15 minutes of baking.

Step 7: Rest, garnish, and serve

Transfer the baked strata to a cooling rack and let it rest for 10–15 minutes before cutting. This brief rest allows the custard to finish setting and makes it easier to slice cleanly into squares.

Just before serving, sprinkle with a little extra fresh thyme or chopped parsley and a few grinds of black pepper for color and aroma. Cut into 8 generous squares and serve warm straight from the baking dish. It pairs beautifully with a simple fruit salad, crisp greens, or a side of bacon for a complete Christmas morning brunch.

Pro Tips

• Use day-old bread: Slightly stale, crusty bread absorbs the custard better and holds its structure, giving you a custardy center with a crisp top.
• Dry the spinach well: Cook off as much moisture as possible from the spinach so the strata does not become watery.
• Let it soak fully: The overnight rest is key for the best texture. If you are in a rush, aim for at least 2–3 hours, but overnight is ideal.
• Check doneness in the center: The edges will set first. Make sure the very middle is no longer jiggly before pulling it from the oven.
• Shred cheese yourself: Freshly shredded Gruyère melts more smoothly and tastes better than pre-shredded cheese.

Variations

• Savory sausage strata: Brown 8–10 oz of breakfast sausage (or crumbled Italian sausage), drain well, and layer it over the first layer of bread before adding the spinach and peppers.
• Mushroom and leek version: Swap the onion for 2 thinly sliced leeks and add 8 oz sliced cremini mushrooms, sautéing them until browned before adding the spinach.
• Cheese swap: Replace half of the Gruyère with sharp white cheddar or fontina for a slightly different flavor profile that is still rich and cozy.

Storage & Make-Ahead

This recipe is designed to be made ahead: assemble the strata completely, cover, and refrigerate for 8–24 hours before baking. Leftover baked strata keeps well in the refrigerator, tightly covered, for up to 3 days. Reheat individual portions in the microwave for 45–60 seconds, or warm larger portions in a 325°F (165°C) oven, covered with foil, for 15–20 minutes until heated through. For longer storage, you can freeze baked strata: cool completely, wrap tightly, and freeze for up to 2 months. Thaw overnight in the refrigerator and reheat in the oven until hot.

Nutrition (per serving)

Approximate values per serving (1/8 of the recipe): about 480 calories; 25 g protein; 30 g fat; 20 g saturated fat; 30 g carbohydrates; 2 g fiber; 6 g sugars; 870 mg sodium. Values will vary based on specific brands and optional ingredients used.