This Chicken and Spinach Breakfast Casserole with Sun-Dried Tomatoes and Feta is a bright, savory start to the day that balances tender chicken, tangy feta, and the concentrated sweetness of sun-dried tomatoes. It’s the sort of recipe you can prep ahead for busy mornings or assemble the night before and bake just before guests arrive. The flavors are Mediterranean-inspired, and the texture is custardy and satisfying without feeling heavy. I love how a few simple pantry staples and fresh greens transform into a crowd-pleasing bake.

Why you’ll love this casserole

Easy to prep: A quick sauté of aromatics and spinach, then everything gets mixed and baked—minimal hands-on time.
Protein-packed: Both whole eggs and egg whites plus cooked chicken make this a filling breakfast or brunch centerpiece.
Bright, balanced flavors: Sun-dried tomatoes add sweetness and depth, while feta brings a salty, creamy contrast.
Make-ahead friendly: Assemble up to 24 hours ahead and refrigerate, then bake when ready.

Ingredients

1 Tbsp avocado oil
1 yellow onion, chopped
4 cloves garlic, minced
5 ounces baby spinach
6 ounces sun-dried tomatoes, drained
4 cups cooked chicken, chopped
6 large eggs
1 16-oz carton egg whites
6 ounces feta cheese
1 tsp sea salt, to taste

Notes about ingredients and swaps

If you’re using store-bought sun-dried tomatoes packed in oil, drain them well and pat dry to avoid excess oil in the custard. For the chicken, rotisserie or leftover roasted chicken works beautifully; just chop it into bite-sized pieces so it distributes through the casserole. If you prefer a milder cheese, you can reduce the feta by an ounce or two, but the 6 ounces give the casserole that pleasing salty tang. Keep the 1 teaspoon of sea salt handy—taste the egg mixture before baking if your feta is particularly salty, and adjust.

Equipment

10×7-inch baking dish or similar-sized casserole dish
Large skillet
Mixing bowl
Whisk or fork
Cutting board and knife

Step-by-step directions

Follow these clear, ordered steps to make the casserole. The sequence follows the original plan: cook aromatics and greens, combine with chicken and tomatoes, whisk the eggs, fold in the cheese, and bake.

Preheat and prepare the dish. Preheat your oven to 375°F (190°C). Lightly oil a 10×7-inch baking dish or spray it with nonstick spray so the casserole releases cleanly after baking.
Sauté the onion. Heat 1 tablespoon avocado oil in a large skillet over medium heat. Add the chopped yellow onion and sauté, stirring occasionally, until it is translucent and beginning to brown at the edges, about 5 to 7 minutes.
Add the garlic. Add the 4 cloves minced garlic to the skillet with the onion and cook for 30 to 60 seconds, stirring constantly, until fragrant. Be careful not to burn the garlic.
Wilt the spinach. Add the 5 ounces baby spinach in batches if necessary, stirring until the spinach fully wilts and any excess moisture has mostly evaporated, about 2 to 3 minutes. Remove the skillet from the heat and let the mixture cool slightly for a minute or two.
Combine chicken and sun-dried tomatoes in the dish. Spread the 4 cups cooked chicken, chopped, evenly in the bottom of the prepared baking dish. Scatter the 6 ounces sun-dried tomatoes, drained and roughly chopped or torn if large, over the chicken.
Add the spinach and onion mixture. Spoon the sautéed onion, garlic, and wilted spinach over the chicken and sun-dried tomatoes, distributing it evenly so every bite will have greens and aromatics.
Whisk the eggs and egg whites. In a large mixing bowl, crack in the 6 large eggs and pour in the 16-oz carton egg whites. Whisk vigorously for 30 to 60 seconds until the mixture is uniformly combined and slightly frothy. Stir in the 1 teaspoon sea salt, then taste a small bit of the raw mixture for seasoning—if your feta is very salty, you may prefer to use a little less salt.
Distribute the feta. Crumble the 6 ounces feta cheese and sprinkle it evenly over the layered ingredients in the baking dish. The feta will melt slightly into the custard and provide pockets of savory flavor.
Pour the egg mixture over the casserole. Carefully pour the whisked eggs and egg whites over the chicken, vegetables, and feta, tilting the dish if needed to help the liquid settle evenly. Use a spatula to nudge any dry pockets so the custard reaches all areas.
Bake until set. Place the casserole in the preheated oven and bake for 30 to 40 minutes, or until the edges are lightly golden and the center is set. To check doneness, insert a knife into the center; it should come out clean or with just a few moist crumbs. Avoid overbaking, which can dry out the eggs.
Rest before serving. Remove the casserole from the oven and let it rest for 8 to 10 minutes. This helps the custard finish setting and makes slicing cleaner.
Slice and serve. Cut the casserole into even squares or wedges. Serve warm, optionally garnished with a sprinkle of extra crumbled feta or a few torn fresh basil leaves for color.

Serving suggestions

This Chicken and Spinach Breakfast Casserole with Sun-Dried Tomatoes and Feta is versatile. Serve it as the star of a brunch spread with a crisp green salad, crusty whole-grain toast, or warm pita. For a lighter accompaniment, a simple cucumber and tomato salad dressed with lemon and olive oil balances the richness. Leftovers are great cold or reheated—slice a square and warm it in the oven at 325°F (160°C) for 10 to 12 minutes or microwave for 60 to 90 seconds.

Make-ahead and storage

To assemble ahead: Follow steps 2 through 9, then cover the uncooked casserole tightly with plastic wrap and refrigerate up to 24 hours. When ready to bake, remove the wrap and bake from chilled; you may need an extra 5 to 10 minutes of oven time.
To store: Refrigerate leftover baked casserole in an airtight container for up to 4 days.
To freeze: Portion the baked casserole into a freezer-safe container for up to 2 months. Thaw overnight in the refrigerator before reheating.

Tips for success

Evenly chopped chicken: Chop cooked chicken into uniform pieces so every bite has an even distribution of protein.
Drain sun-dried tomatoes well: Excess oil or liquid from sun-dried tomatoes can make the custard runny. Pat them dry with paper towels if necessary.
Don’t overcook: The casserole will continue to set while resting. Take it out of the oven when the center is just set to avoid rubbery eggs.
Adjust salt carefully: Because feta adds saltiness, taste the egg mixture before adding the full teaspoon if you’re sensitive to sodium.

Nutrition snapshot

This casserole is a balanced, protein-forward meal thanks to eggs, egg whites, and chicken. The spinach provides iron and vitamins, and sun-dried tomatoes and feta contribute potassium, calcium, and flavor without excess fuss. Nutrition will vary based on specific brands and portion sizes; consider checking labels if you track calories or macros closely.

Variations to try

Herby version: Stir in chopped dill, parsley, or basil for a fresh note that pairs nicely with feta.
Spicy kick: Add a pinch of red pepper flakes to the sautéed onion and garlic, or top with sliced jalapeños before baking.
Vegetable-packed: Fold in diced bell peppers or mushrooms with the onion if you want more vegetables in each slice.
Cheesy swap: Replace half the feta with shredded mozzarella for a milder, melty texture while keeping the feta’s briny highlights.

Final thoughts

This Chicken and Spinach Breakfast Casserole with Sun-Dried Tomatoes and Feta hits that sweet spot between make-ahead convenience and fresh flavor. It’s forgiving, adaptable, and satisfying whether you’re feeding a family, prepping breakfasts for the week, or hosting a relaxed weekend brunch. The combo of tender chicken, savory feta, and sweet sun-dried tomatoes turns a simple egg casserole into something you’ll want to make again and again.

Happy baking—may your mornings be filled with delicious, easy-to-serve food that keeps life flavorful and fuss-free.

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Chicken and Spinach Breakfast Casserole with Sun-Dried Tomatoes and Feta

A savory, make-ahead breakfast casserole with chicken, spinach, sun-dried tomatoes, and feta that bakes into a golden, protein-packed morning meal.

Prep Time15

Cook Time35

Total Time50

Servings: 8 servings

Ingredients

1 Tbsp avocado oil
1 yellow onion chopped
4 cloves garlic minced
5 ounces baby spinach
6 ounces sun-dried tomatoes drained
4 cups cooked chicken chopped
6 large eggs
1 16-oz carton egg whites
6 ounces feta cheese
1 tsp sea salt or to taste

Instructions

Preheat the oven to 375°F (190°C) and spray a 13 x 9-inch casserole dish with cooking spray.
Heat the avocado oil in a large skillet over medium-high heat. Add the chopped onion and sauté, stirring occasionally, until it begins to soften, about 5–8 minutes.
Add the minced garlic and baby spinach to the skillet, cover, and cook until the spinach wilts, about 2 minutes; then stir in the drained sun-dried tomatoes and season with sea salt. Remove from heat.
Transfer the chopped cooked chicken to the prepared casserole dish and spread into an even layer. Top with the sautéed vegetable and tomato mixture.
In a large bowl, whisk together the 6 whole eggs and the 16-oz carton of egg whites until well combined, seasoning with additional salt if desired.
Pour the egg mixture evenly over the chicken and vegetables in the casserole dish, then sprinkle the feta cheese over the top and gently stir slightly to distribute.
Bake on the center rack for 35–45 minutes, or until the top is golden and a knife inserted in the center comes out clean; internal temperature should reach about 190°F (88°C) if using a thermometer.
Let the casserole cool for at least 10 minutes before slicing and serving.