Strata is one of those recipes that makes mornings feel calm even when they’re not. You do the work the night before, sleep a little better, and wake up to a casserole that bakes into golden, custardy goodness. This Vegetarian Overnight Breakfast Strata keeps things simple: sautéed vegetables, shredded cheddar, and a rich egg-and-milk custard soaking into soft white bread.

I test recipes with real schedules in mind — weeknights that stretch into evenings and weekend brunches with guests. This strata fits both. It’s forgiving, feeds a crowd, and travels well to potlucks or sleepy Sunday tables. Follow the steps and the dish will do most of the heavy lifting for you.

Below you’ll find exactly what I used, the official step-by-step directions, swaps, troubleshooting tips, and storage notes so you can make it with confidence. Let’s get into it.

What We’re Using

Ingredients

1 tablespoon olive oil — for sautéing the vegetables and adding a light layer of fat to the dish so the bottom doesn’t stick.
1 cup chopped onion (about 1 small onion) — provides sweetness and depth when softened.
1 cup chopped green bell pepper (about 1 medium green bell pepper) — adds color and a bit of bite; chop uniformly for even cooking.
1 cup white button mushrooms (sliced) — give an earthy note and hold up well in the custard.
9 eggs — the structure of the strata; whisk until blended for an even custard.
3 cups whole milk (unsweetened oat milk also works) — creates the custard. Note: a plant milk alternative is acceptable if labeled unsweetened.
3/4 teaspoon kosher salt — seasons the custard and brings other flavors forward.
1/4 teaspoon freshly ground black pepper — offers a gentle heat; use freshly ground for the best aromatic quality.
12 slices white bread (crusts removed) — the base that soaks up the custard; remove crusts for a more uniform texture.
10 ounces medium cheddar cheese, shredded (about 2 1/2 cups) — melts into pockets of savory richness throughout the strata.
parsley (minced, for garnish) — brightens the finished dish; sprinkle just before serving.

How to Prepare (Vegetarian Overnight Breakfast Strata)

Heat 1 tablespoon olive oil in a medium sauté pan over medium heat. Add the chopped onion, chopped green bell pepper, and sliced mushrooms and cook, stirring occasionally, until softened, about 7–8 minutes. Remove from heat and set aside to cool slightly.
In a medium bowl, whisk the 9 eggs until blended. Add the 3 cups milk, 3/4 teaspoon kosher salt, and 1/4 teaspoon freshly ground black pepper; whisk until combined.
Prepare a 9″x13″ casserole dish. If there is any oil left in the sauté pan, pour it into the dish and tilt to lightly coat the bottom and sides.
Arrange half of the bread slices (6 slices) in a single layer to cover the bottom of the dish, tearing slices as needed to fit.
Evenly sprinkle half of the cooked vegetables over the bread, then evenly sprinkle half of the shredded cheddar cheese.
Pour half of the egg mixture evenly over the first layer of bread, vegetables, and cheese. Press the bread gently so it absorbs the liquid and any floating pieces become submerged.
Repeat the layers: place the remaining 6 bread slices in a single layer, top with the remaining vegetables, then the remaining cheese, and pour the remaining egg mixture evenly over everything. Press gently again to submerge any floating bread.
Cover the dish tightly and refrigerate for at least 3 hours or up to overnight to allow the bread to soak.
When ready to bake, preheat the oven to 350 degrees Fahrenheit. Uncover the casserole and bake uncovered for about 50 minutes, until the center is set and no longer jiggly.
Let the strata rest for a few minutes, garnish with minced parsley, cut into squares, and serve.

Why You’ll Love This Recipe

This strata is comforting without being heavy. The texture hits a sweet spot: crisp edges, a soft but set center, and cheesy pockets where the cheddar melted into crevices. It’s also adaptable — mild flavors that pair with lots of sides: a green salad, fruit, or a dollop of salsa if you like a little brightness.

You’ll appreciate how forgiving it is. The overnight soak gives the bread a chance to fully absorb liquid, so even if you don’t get perfect timing the next morning, the custard still bakes up evenly. It feeds a group and scales up or down easily, and because it’s vegetarian, it’s a crowd-pleaser for varied diets.

Swap Guide

Milk: The recipe notes unsweetened oat milk as an alternative. Use it if you need dairy-free; make sure it’s unsweetened to avoid off-flavors.
Bread: If you prefer more structure, replace white bread with a sturdier loaf (sourdough, country loaf) — tear to fit the dish. Denser breads need a slightly longer soak to hydrate fully.
Cheese: If medium cheddar isn’t your favorite, try a sharper cheddar or a blend with Monterey Jack for a milder melt. Use the same volume (about 10 ounces shredded).
Vegetables: Keep similar-volume vegetables. If you swap in spinach or tomatoes, squeeze excess moisture from spinach and pat tomatoes dry to prevent a soggy center.

Prep & Cook Tools

Medium sauté pan — for softening the vegetables so they don’t release too much water into the strata.
Medium bowl and whisk — to combine the eggs, milk, and seasoning until smooth.
9″x13″ casserole dish — the size specified in the recipe; it gives the strata the right depth for even baking.
Cheese grater — for shredding the cheddar so it melts evenly.
Plastic wrap or foil — to cover the dish tightly while it soaks in the refrigerator.
Oven thermometer (optional) — helpful if your oven runs hot or cool; it ensures you bake at a reliable 350°F.

Errors to Dodge

Overfilling the dish — use a 9″x13″ as directed. A smaller pan will spill and a much deeper pan changes cook time.
Skipping the cool-down for the vegetables — pouring very hot vegetables into the egg mixture can start cooking the eggs prematurely and create curdled spots.
Not pressing the bread down — if you don’t press to submerge, some bread will float and dry out instead of becoming custardy.
Baking before the center is set — test the center gently; it should no longer be jiggly. Undercooked custard will be runny when cut.
Using watery add-ins without adjustment — high-moisture veg (like fresh tomatoes) need draining or roasting first to avoid a soggy strata.

In-Season Swaps

Spring: Add thinly sliced asparagus tips and ramps (or scallions) for fresh, green flavor. Sauté briefly before layering.
Summer: Use small-diced bell peppers or roasted sweet peppers that have been drained of excess oil. Add zucchini slices that have been salted and patted dry.
Fall: Stir in sautéed shallots and chopped roasted squash; both bring warmth and heartiness.
Winter: Swap in sautéed leeks and mushrooms for a cozy, savory combination.

Author’s Commentary

I make this strata when I want cooking to feel like a small, contained project rather than an all-morning production. The prep is honest and uncluttered: chop, sauté, whisk, layer, and sleep on it. The next day you get the reward — a hot, comforting dish and fewer decisions at breakfast time.

One habit I developed is to sauté the veg with a pinch more salt than I think I need. Vegetables often need a bit of extra seasoning to shine once mixed with bread and custard. Taste as you go, but remember the recipe already includes 3/4 teaspoon kosher salt in the custard, so balance accordingly.

Save for Later: Storage Tips

Refrigerating

Cool any leftovers to room temperature, then cover tightly and refrigerate for up to 3–4 days. Reheat individual squares in a 350°F oven for 10–15 minutes or microwave slices in short bursts until warmed through.

Freezing

You can freeze baked strata. Slice into portions, wrap each piece tightly in plastic wrap and foil, and freeze for up to 2 months. Thaw overnight in the refrigerator before reheating in a 350°F oven until warmed through (about 20–30 minutes depending on thickness).

Make-ahead variations

As the recipe directs, you can assemble and refrigerate for up to overnight before baking. If you need to prepare further ahead, assemble and freeze the unbaked, covered casserole. Thaw overnight in the fridge, then bake as instructed, adding a few extra minutes if needed until the center sets.

Common Questions

Can I use day-old bread? Yes. Slightly stale bread actually soaks up the custard better and helps give a more uniform texture.
Do I need to pre-cook the vegetables? Yes — the recipe calls for sautéing the onion, pepper, and mushrooms until softened. Raw vegetables will release water and won’t develop the same depth of flavor.
Can I make this dairy-free? Use an unsweetened plant milk like oat milk (noted in the ingredients). For cheese, use a dairy-free shredded alternative if needed, though texture and flavor will differ.
How do I know when it’s done? The center should be set and not jiggly. The top will be lightly golden and the edges slightly puffed.
Can I add herbs or spices? Yes. Fresh thyme, chives, or a pinch of smoked paprika are good additions. Add fresh herbs after baking or sprinkle on top before serving for maximum flavor.

Wrap-Up

Follow the steps and you’ll have a dependable, crowd-friendly strata that makes mornings easier and brunches better. It stores and reheats well, adapts to seasonal produce, and is forgiving for cooks who want solid results with minimal stress. Make it the night before, sleep a little easier, and enjoy the reward when your oven dings.

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Vegetarian Overnight Breakfast Strata

A make-ahead vegetarian overnight strata with sautéed vegetables, cheddar, and bread soaked in an egg-milk mixture; refrigerate 3 hours or overnight and bake until set.

Prep Time25

Cook Time45

Total Time1 10

Course: Breakfast

Servings: 12 servings

Ingredients

1 tablespoonolive oil
1 cupchopped onion about 1 small onion
1 cupchopped green bell pepper about 1 medium green bell pepper
1 cupwhite button mushrooms sliced
9 eggs
3 cupswhole milk unsweetened oat milk also works
3/4 teaspoonkosher salt
1/4 teaspoonfreshly ground black pepper
12 sliceswhite bread crusts removed
10 ouncesmedium cheddar cheese shredded(about 2 1/2 cups)
parsley minced, for garnish

Instructions

Heat 1 tablespoon olive oil in a medium sauté pan over medium heat. Add the chopped onion, chopped green bell pepper, and sliced mushrooms and cook, stirring occasionally, until softened, about 7–8 minutes. Remove from heat and set aside to cool slightly.
In a medium bowl, whisk the 9 eggs until blended. Add the 3 cups milk, 3/4 teaspoon kosher salt, and 1/4 teaspoon freshly ground black pepper; whisk until combined.
Prepare a 9"x13" casserole dish. If there is any oil left in the sauté pan, pour it into the dish and tilt to lightly coat the bottom and sides.
Arrange half of the bread slices (6 slices) in a single layer to cover the bottom of the dish, tearing slices as needed to fit.
Evenly sprinkle half of the cooked vegetables over the bread, then evenly sprinkle half of the shredded cheddar cheese.
Pour half of the egg mixture evenly over the first layer of bread, vegetables, and cheese. Press the bread gently so it absorbs the liquid and any floating pieces become submerged.
Repeat the layers: place the remaining 6 bread slices in a single layer, top with the remaining vegetables, then the remaining cheese, and pour the remaining egg mixture evenly over everything. Press gently again to submerge any floating bread.
Cover the dish tightly and refrigerate for at least 3 hours or up to overnight to allow the bread to soak.
When ready to bake, preheat the oven to 350 degrees Fahrenheit. Uncover the casserole and bake uncovered for about 50 minutes, until the center is set and no longer jiggly.
Let the strata rest for a few minutes, garnish with minced parsley, cut into squares, and serve.

Equipment

Sauté Pan
9x13 Inch Casserole Dish
Mixing Bowl
Whisk

Notes

1 tablespoon olive oil
1/2 cup chopped onion
1/2 cup chopped green pepper
3/4 cup white button mushrooms
6 eggs
2 cups half and half
1/2 teaspoon salt
Fresh ground pepper
8 slices white bread (crusts removed)
2 cups cheddar cheese, shredded
1/2 pound sausage
In a medium saute pan, heat the olive oil and saute the onion, green pepper, and mushrooms until soft, about 7-8 minutes. Set aside.
If using sausage, brown it in a medium saute pan and drain.
If using veggie sausage, heat it in the microwave for a minute or so and crumble.
In a medium bowl, whisk the eggs, half and half, salt, and pepper.
Spray two approximately 4″ x 8” baking pans/casserole dishes with non-stick cooking spray.
Layer two slices of the bread in the bottom of each pan.
Sprinkle 1/4 of the veggies over the bread in each pan.
Spread half the crumbled sausage over the sausage version.
Sprinkle on 1/4 of the cheese over each.
Pour about 1/2 cup of the egg mixture over the top.
Add a layer of the remaining bread, two more slices each, then veggies, then sausage over the sausage side, then cheese.
Pour the rest of the egg mixture evenly over the top of each.
Cover tightly and refrigerate overnight, or for at least three hours.
In the morning, uncover and bake at 325 degrees for about 40 – 50 minutes, until set.