Crispy Onion Broccoli Egg Casserole

Crispy Onion Broccoli Egg Casserole

This vegetable casserole combines broccoli, mushrooms, bell pepper, eggs, and cheddar under a measured crisp-onion topping. Precooking the vegetables removes water that could weaken the egg set, while adding the onions late keeps them crisp instead of scorched.

Recipe details

• Yield: 6 servings
• Prep: 20 minutes
• Bake: 30–37 minutes
• Equipment: knife, cutting board, large skillet, spatula, bowl, whisk, 8-inch square ceramic baking dish, instant-read thermometer

Ingredients

• 1 tablespoon olive oil
• 3 cups small broccoli florets
• 8 ounces cremini mushrooms, sliced
• 1 red bell pepper, diced
• 1/2 teaspoon fine salt, divided
• 1/4 teaspoon black pepper
• 8 large eggs
• 1/2 cup whole milk
• 1 teaspoon Dijon mustard
• 1 cup shredded sharp cheddar cheese
• 3/4 cup packaged crispy fried onions, divided

Method

1. Heat the oven to 350°F. Lightly oil the baking dish.
2. Warm olive oil in the skillet over medium-high. Add broccoli, mushrooms, bell pepper, 1/4 teaspoon salt, and pepper. Cook 8–10 minutes, stirring, until broccoli is bright and nearly tender and no liquid remains. Cool for 5 minutes.
3. Whisk eggs, milk, mustard, and remaining 1/4 teaspoon salt until no white streaks remain. Stir in cheddar, the cooked vegetables, and 1/2 cup crispy onions.
4. Spread in the dish and bake 25–30 minutes, until the edges are set but the center still has a slight unified wobble.
5. Scatter the remaining 1/4 cup onions over the surface. Bake 5–7 minutes more, until the topping is crisp, no liquid egg appears, and several points in the center reach 160°F.
6. Rest 10 minutes before cutting into six rectangles.

Functions and doneness cues

Eggs form the casserole’s structure, milk softens the set, and cheddar adds fat and flavor. Mustard sharpens the cheese without adding much liquid. Mushrooms and bell pepper release substantial moisture, so the skillet should look dry before they leave it. The onion topping contributes salt, texture, and browned flavor.

The casserole may puff near the edges and settle during the rest. Judge doneness at the center: it should move as one piece, feel resilient, and meet the temperature endpoint. Deep browning alone is not proof that the egg interior is safe.

Troubleshooting and substitutions

A watery casserole usually means the vegetables were crowded or insufficiently cooked; evaporate their liquid before mixing. If onions darken too quickly, tent loosely with foil. If the center remains below 160°F, continue in 2-minute intervals. A rubbery edge indicates overbaking or a metal pan that heated faster than the specified ceramic dish.

Cauliflower florets may replace broccoli if cut equally small. Monterey Jack can replace cheddar. Thawed frozen broccoli is usable only after squeezing it dry and reducing the skillet time. Fresh raw onion is not a direct substitute for packaged crispy onions because it supplies moisture rather than crunch.

Storage and safety

Refrigerate within 2 hours at 40°F or below and use within 4 days. Reheat portions to 165°F. Freeze cooled portions airtight for up to 1 month; thaw in the refrigerator. Discard casserole left out longer than 2 hours, or 1 hour above 90°F. Review fried-onion labels for wheat and other allergens.