How many servings does this recipe make?

This recipe makes 4 servings. You can adjust the portion size directly on this page.

What ingredients do I need for Portabella Breakfast Casserole?

You need 10 ingredients. The key ingredients include: 2 cups chopped portabella mushrooms, 2 medium garlic cloves, minced, 12 small red onion, sliced, 1 teaspoon chopped fresh rosemary, and more.

Is Portabella Breakfast Casserole suitable as breakfast?

Yes, Portabella Breakfast Casserole falls under the Breakfast category and is a great choice for this type of meal.

How do I store leftover Portabella Breakfast Casserole?

Store leftovers in an airtight container in the refrigerator for up to 3–4 days. Reheat gently before serving.

Portabella Breakfast Casserole Recipe

Name: Portabella Breakfast Casserole
Prep time: 15 min
Cook time: 30 min
Total time: 45 min
Yield: 4 servings
Ingredients: 2 cups chopped portabella mushrooms; 2 medium garlic cloves, minced; 12 small red onion, sliced; 1 teaspoon chopped fresh rosemary; 2 slices light whole wheat bread, cut into small cubes (not grainy); 4 ounces low-fat cheddar cheese, finely grated; 2 cups egg substitute (or 8 eggs); ¼ cup low-fat milk; ¼ teaspoon salt; ¼ teaspoon pepper

Start your day right with this Portabella Breakfast Casserole recipe. Made with portabella mushrooms, garlic, red onion and rosemary. Easy step-by-step …

This Portabella Breakfast Casserole relies on simple, everyday ingredients such as chopped portabella mushrooms, medium garlic cloves, minced, small red onion, sliced and chopped fresh rosemary. It comes together quickly and makes 4 servings, at about 455 kcal each. The step-by-step instructions below are written to be easy to follow, even on a busy day.

It's an easy way to start the day, whether you're cooking a relaxed weekend breakfast or need something satisfying before a busy morning. Pair it with fresh fruit or your favorite hot drink to round out the meal.

Updated Jun 30, 2026

Serves 4 Breakfast

Tips for the best results

Read through all the steps once before you start and measure out your ingredients first — it makes everything go more smoothly.
Taste as you go and adjust the seasoning before serving.
Avoid overcrowding the pan — cook in batches if needed for the best texture.
Let the dish rest for a few minutes before serving so the flavors settle.
Store leftovers in an airtight container in the fridge and enjoy within a few days.

Variations & substitutions

Feel free to swap in similar ingredients you already have on hand and adjust seasoning to taste.

No specific allergen information. Please check the ingredient list for possible allergens.

My Personal Notes

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Portabella Breakfast Casserole

Tips for the best results

Variations & substitutions

My Personal Notes

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