Prep Time: 25 minutes
Cook Time: 55 minutes
Inactive Time (Chilling): 30 minutes (optional but recommended)
Total Time: 1 hour 50 minutes (including chill time)
Servings: 8
Course: Breakfast, Brunch, Main Course
Cuisine: American
Recipe Intensity:
Effort Level: Easy
Skill Level: Beginner
Active Hands-On Time: Medium (25 mins of chopping and mixing)
A Vibrant, Make-Ahead Marvel
Say goodbye to boring breakfasts! This Garden Harvest Egg & Vegetable Casserole is a celebration of seasonal produce baked into a fluffy, protein-packed dish. Designed for convenience and health, it’s the ultimate solution for feeding a crowd at Sunday brunch or streamlining your busy weekday mornings. By combining sautéed onions, peppers, and spinach with golden potatoes and a rich egg custard, every bite delivers a perfect balance of flavor and texture. The best part? Assemble it the night before, pop it in the oven when you wake up, and let the delicious aroma fill your kitchen.
Ingredients
For the Vegetable Base:
1 tablespoon olive oil
1 medium yellow onion, diced
1 red bell pepper, diced
1 cup cremini mushrooms, sliced
2 cups fresh baby spinach, loosely packed
3 cups frozen shredded hash browns (thawed), or 2 cups diced, parboiled Yukon gold potatoes
3 cloves garlic, minced
1 teaspoon dried thyme
½ teaspoon smoked paprika
Salt and black pepper to taste
For the Egg Custard:
8 large eggs
1 ½ cups whole milk (or 2% for a lighter option)
½ cup heavy cream or full-fat coconut milk (for richness)
1 teaspoon Dijon mustard
1 teaspoon fine sea salt
½ teaspoon black pepper
For the Add-Ins & Topping:
1 ½ cups shredded sharp cheddar cheese, divided
½ cup crumbled feta cheese (optional, for tang)
2 tablespoons chopped fresh chives or parsley, for garnish
Equipment
9×13 inch baking dish
Large skillet
Mixing bowls
Whisk
Measuring cups and spoons
Step-by-Step Instructions
1. Sauté the Vegetables:
Heat olive oil in a large skillet over medium heat. Add the diced onion and bell pepper. Cook for 5-7 minutes until softened. Add the mushrooms and cook for another 5 minutes until they release their moisture. Stir in the minced garlic, thyme, smoked paprika, and a pinch of salt and pepper. Cook for 1 minute until fragrant. Finally, add the spinach and stir until just wilted, about 1-2 minutes. Remove from heat and let cool slightly.
2. Prepare the Baking Dish:
Grease your 9×13 inch baking dish with butter or cooking spray. Spread the thawed hash browns or parboiled potatoes evenly across the bottom. This creates a sturdy, comforting base.
3. Layer the Fillings:
Spoon the sautéed vegetable mixture evenly over the potato layer. Sprinkle 1 cup of the shredded cheddar cheese and all of the feta (if using) over the vegetables.
4. Make the Egg Custard:
In a large mixing bowl, whisk the eggs vigorously until well blended and slightly frothy. Add the milk, cream, Dijon mustard, salt, and pepper. Whisk until the mixture is completely homogeneous and smooth.
5. Assemble & Chill (The Key Step!):
Slowly and carefully pour the egg custard over the layered vegetables and cheese in the baking dish. Gently tap the dish on the counter to allow the custard to settle into all the gaps. Sprinkle the remaining ½ cup of cheddar cheese on top.
Pro-Tip: At this point, you can cover the dish tightly with plastic wrap and refrigerate for 30 minutes up to overnight. This allows the eggs to soak into the ingredients, resulting in a more cohesive and flavorful casserole.
6. Bake to Perfection:
Preheat your oven to 375°F (190°C). Place the casserole dish (uncovered) on the middle rack. Bake for 50-60 minutes. The casserole is done when the edges are golden brown, the center is set (with only a slight jiggle), and a knife inserted near the center comes out clean.
7. Rest and Serve:
Remove the casserole from the oven and let it rest for 10 minutes before slicing. This crucial step allows the proteins to set, making it easier to cut into clean squares. Garnish with freshly chopped chives or parsley. Serve warm.
Make-Ahead & Storage Instructions
Make-Ahead: Follow steps 1-5. Cover and refrigerate for up to 24 hours before baking. You may need to add 5-10 minutes to the baking time if starting from cold.
Storage: Allow leftovers to cool completely. Store in an airtight container in the refrigerator for up to 4 days.
Reheating: Reheat individual portions in the microwave for 60-90 seconds, or cover the whole casserole with foil and warm in a 325°F (165°C) oven for 15-20 minutes.
Freezing: Bake and cool the casserole completely. Wrap individual slices or the entire dish tightly in plastic wrap and then foil. Freeze for up to 2 months. Thaw overnight in the refrigerator before reheating.
Customization Ideas
Protein Power: Add 1 cup of cooked, crumbled breakfast sausage, diced ham, or cooked bacon.
Veggie Swap: Use zucchini, broccoli florets, or sun-dried tomatoes instead of mushrooms or peppers.
Dairy-Free: Use unsweetened almond milk, omit the cream, and use a dairy-free cheese alternative.
Lower-Carb: Substitute the potatoes with 3 cups of cauliflower rice (sautéed first to remove moisture).
Nutrition Information
(Per serving, based on 8 servings, calculated with whole milk, heavy cream, and all cheeses.)
Calories: ~320 kcal
Total Fat: 22g
Saturated Fat: 11g
Cholesterol: 235mg
Sodium: 680mg
Total Carbohydrates: 15g
Dietary Fiber: 2g
Sugars: 4g
Protein: 18g