I’ve been making this overnight veggie and cheese casserole for years when I need a no-fuss brunch or an easy weeknight dinner that feeds a crowd. It’s a savory, make-ahead bake that soaks up flavor overnight, then turns into fluffy, golden slices the next day perfect for busy mornings, potlucks, and lazy weekends. If you enjoy ready-to-bake breakfast casseroles, you might also like this overnight sausage and egg casserole as another easy overnight option.
Why you’ll love this dish
This casserole hits a lot of home-cooking sweet spots. It’s economical, using simple produce and day-old bread to stretch ingredients. Prep is quick about 15 to 20 minutes and the overnight soak does the work for you while you sleep. Kids and picky eaters often like the familiar texture and melty cheese, and it’s flexible: swap cheeses, use whatever vegetables are in the fridge, or make it dairy-free with plant milk and vegan cheese. It’s ideal for brunch spreads, school-week dinners, or when you want a ready-to-reheat breakfast that tastes homemade.
The cooking process explained
Quick overview so you know what to expect: chop the vegetables and cube the bread, whisk eggs with milk and seasonings, pour the egg mixture over the bread and veg, fold in most of the cheese, then refrigerate overnight so the bread soaks up the custard. Next day you bake at 350°F until set and golden, let it rest a few minutes, then slice. It’s basically an overnight strata with bright veggies and gooey cheese.
What you’ll need
- 1 cup diced bell peppers (any color)
- 1 cup diced onions
- 1 cup diced tomatoes (seeds removed) pat dry so the casserole isn’t too wet
- 2 cups chopped fresh spinach loosely packed
- 1 cup shredded cheese (cheddar, mozzarella, or a mix) reserve a few tablespoons for the top
- 6 large eggs
- 1 cup milk (dairy or unsweetened plant milk) use unsweetened almond, oat, or soy if dairy-free
- 1 teaspoon salt
- 1/2 teaspoon black pepper
- 1 teaspoon garlic powder
- 1 teaspoon onion powder
- 1 loaf of bread, cubed (day-old or slightly stale) sourdough, French, or a hearty sandwich loaf works well
Ingredient notes: use gluten-free bread to make this gluten-free. For a lighter texture use more airy bread; for a denser custard use denser bread. If you prefer more vegetables, increase the spinach or peppers slightly and reduce bread by a cup.
Step-by-step instructions
- Preheat nothing yet. In a large bowl combine the diced bell peppers, diced onions, seeded tomatoes, chopped spinach, and cubed bread. Toss gently to spread the bread pieces.
- In a separate bowl whisk together the eggs, milk, salt, black pepper, garlic powder, and onion powder until smooth and a little frothy.
- Pour the egg mixture evenly over the bread and vegetables. Stir gently so liquid coats all bread cubes. Press down lightly with a spatula to encourage absorption.
- Fold in most of the shredded cheese, keeping a small handful to sprinkle on top for a golden crust.
- Cover the bowl with plastic wrap and refrigerate for at least 6 to 12 hours so the bread fully soaks the custard.
- When ready to bake, preheat oven to 350°F (175°C). Grease a baking dish and transfer the soaked mixture into it, smoothing the top and sprinkling the reserved cheese.
- Bake for 30 to 35 minutes, until the center is set and the top is golden brown. A toothpick inserted in the center should come out mostly clean; the internal temperature should reach about 160°F (71°C) for safety.
- Let the casserole rest 5 to 10 minutes before slicing; resting yields cleaner pieces.
Best ways to enjoy it
Serve warm, cut into squares. It pairs nicely with a crisp green salad, a bowl of fresh fruit, or roasted potatoes. For a heartier brunch plate, offer a side of sautéed mushrooms or grilled tomatoes. If you want complementary casseroles on the table, a savory rice bake like a cheesy ground beef and rice casserole works well for larger gatherings the two dishes balance each other in texture and flavor.
Storage and reheating tips
Cool leftovers to room temperature no longer than two hours, then refrigerate in an airtight container for up to 4 days. To reheat, place slices in a single layer on a baking sheet, cover loosely with foil, and warm at 325°F until heated through, about 10 to 15 minutes. You can also microwave single portions on medium power in 30-second bursts until warm. To freeze: wrap individual slices in plastic wrap and place in a freezer-safe bag for up to 3 months. Thaw overnight in the fridge and reheat as above. Always reheat until steaming hot and check that internal temperature reaches at least 165°F for leftover safety.
Pro chef tips
- Use day-old bread; it soaks custard without turning to mush. If your bread is fresh, toast cubes lightly before mixing.
- Squeeze excess moisture from seeded tomatoes and spinach pressed in a colander or wrapped in a clean towel to avoid a soggy center.
- Don’t over-soak: 6 to 12 hours is ideal. Overnight is convenient, but if it sits much longer the texture can become too dense.
- If you like a crisp top, broil for 1 to 2 minutes at the end of baking while watching closely.
- For even baking, spread the mixture in a pan no deeper than 2 inches; deeper dishes may need extra baking time.
Creative twists
- Add roasted red peppers, chopped zucchini, or caramelized onions for extra depth.
- Swap cheeses: pepper jack adds heat, feta adds tang, or a smoked cheese adds richness.
- Make it vegetarian-friendly by adding cooked lentils or crumbled firm tofu for extra protein.
- For a low-carb version, replace bread with thinly sliced roasted potatoes or omit bread and bake as a crustless vegetable frittata (reduce baking time slightly).
- To make mini portions, fill a greased muffin tin and bake 18 to 22 minutes for grab-and-go servings.
Common questions
How long does it take to assemble and how much hands-on time is needed?
Hands-on time is about 15 to 20 minutes: chop vegetables, cube the bread, whisk the custard, mix and refrigerate. Overnight chilling requires at least 6 hours, but 8 to 12 hours is best.
Can I shorten the chilling time and still bake the casserole?
Yes. If you’re short on time, let the mixture sit for 1 to 2 hours at room temperature or 2 to 3 hours in the fridge, but the texture will be less custardy and more bread-pudding–like. For best results, plan the overnight soak.
Are there good substitutions for eggs or dairy?
For dairy-free, use unsweetened plant milk and dairy-free shredded cheese. For an egg-free version, try blending silken tofu until smooth and seasoning it; texture will differ and baking times may vary. This dish is naturally adaptable, but replacing eggs entirely changes the structure.
Can I prepare and freeze this before baking?
Yes, assemble in a freezer-safe dish, cover tightly, and freeze for up to 3 months. Thaw overnight in the refrigerator before baking, then bake at 350°F until set, adding a few extra minutes if still slightly cold.
How do I know when the casserole is fully cooked?
The center should be set and not jiggly. A toothpick should come out mostly clean. For food safety, aim for an internal temperature around 160°F (71°C).
Overnight Veggie and Cheese Casserole
Ingredients
Method
- In a large bowl, combine the diced bell peppers, diced onions, seeded tomatoes, chopped spinach, and cubed bread. Toss gently to spread the bread pieces.
- In a separate bowl, whisk together the eggs, milk, salt, black pepper, garlic powder, and onion powder until smooth and a little frothy.
- Pour the egg mixture evenly over the bread and vegetables. Stir gently so liquid coats all bread cubes. Press down lightly with a spatula to encourage absorption.
- Fold in most of the shredded cheese, keeping a small handful to sprinkle on top for a golden crust.
- Cover the bowl with plastic wrap and refrigerate for at least 6 to 12 hours.
- When ready to bake, preheat the oven to 350°F (175°C). Grease a baking dish and transfer the soaked mixture into it, smoothing the top and sprinkling the reserved cheese.
- Bake for 30 to 35 minutes, until the center is set and the top is golden brown.
- Let the casserole rest for 5 to 10 minutes before slicing.
