Weekday mornings are busy, but breakfast shouldn’t be ignored—or boring. This casserole is the kind of make-ahead, hands-off dish that feels thoughtful and tastes like you actually tried. It’s sturdy, bright, and forgiving: eggs, milk, cream, a big handful of spinach, tangy feta, mild shallots, scallions, and juicy diced tomatoes come together into a skillet-to-bake dish that slices well and keeps you full.

I love bringing this to the weekend brunch table or prepping it on Sunday for easy warm breakfasts all week. The texture stays tender because of the milk and cream. The feta gives a salty lift without needing much extra seasoning. And the spinach and tomatoes add color and real vegetable uptake—no pretending here.

Below you’ll find the ingredients laid out with quick role notes, the exact step-by-step method to follow, and practical tips for swaps, troubleshooting, and storage. Read through once, then cook. It’s straightforward, reliable, and exactly what a weekday-morning casserole should be.

What Goes In

olive oil spray — for coating the baking dish so the casserole releases easily.
1 teaspoon olive oil — used to soften the shallots and carry flavor.
3 shallots, chopped — mellow, sweet aromatics that build the base flavor.
6 ounce bag baby spinach — the green component; wilts down and adds volume without overpowering.
24 large eggs, beaten — the structure and protein for the casserole.
2 cups 2% milk — keeps the custard light while adding moisture.
1/2 cup heavy cream — lifts richness and helps a tender texture.
12 ounces Feta cheese, crumbled — salty, tangy focal point; evenly distributed in the custard.
3 scallions, chopped — fresh bite and mild onion flavor scattered through the bake.
3 plum tomatoes, seeded and diced — add juiciness and brightness without too much moisture when seeded.
2 1/2 teaspoons kosher salt — purposeful seasoning to bring out flavors in the large egg batch.
black pepper, to taste — finishing spice; add at the end or at serving.

Stepwise Method: Healthy Breakfast Casserole with Spinach and Feta

Preheat the oven to 350°F. Spray a 9 x 13 x 3-inch Pyrex deep baking dish with olive oil spray and set it aside.
Heat a large skillet over medium heat. Add 1 teaspoon olive oil.
Add the chopped shallots to the skillet and cook, stirring occasionally, until soft and translucent, about 6 to 8 minutes.
Add the 6-ounce bag of baby spinach to the skillet and cook, stirring, until the spinach is fully wilted, about 2 to 4 minutes. Remove the skillet from the heat.
Transfer the cooked spinach and shallots to a bowl or plate and press with a spatula or spoon to remove excess liquid. Set aside to cool briefly.
In a large bowl, whisk the 24 beaten eggs, 2 cups 2% milk, and 1/2 cup heavy cream until blended.
Stir the 12 ounces crumbled Feta, 3 chopped scallions, 3 seeded and diced plum tomatoes, 2 1/2 teaspoons kosher salt, and black pepper to taste into the egg mixture until evenly combined.
Fold the cooked spinach and shallots into the egg mixture until evenly distributed.
Pour the mixture into the prepared baking dish and smooth the top gently.
Bake in the preheated oven until the center is set and cooked through, about 1 hour 20 minutes. A knife inserted into the center should come out clean.
Remove from the oven and let the casserole rest for 10–15 minutes before slicing and serving.

Why This Recipe Belongs in Your Rotation

This casserole hits three practical marks: it’s make-ahead friendly, crowd-pleasing, and nutrient-dense. Twenty-four eggs make a substantial, protein-forward base that will keep you satisfied. The dairy combo of milk and cream creates a tender custard rather than a rubbery texture—small detail, big difference.

It’s flexible too. Bring it to brunch, slice and store for weekday reheats, or portion into lunches. The flavors are broad-appeal: mild shallots, bright tomatoes, pop of scallion, and salty feta—no single ingredient dominates, but together they make a memorable bite.

Finally, the method is forgiving. Wilt the spinach until just soft, press out excess moisture, and you avoid a soggy bake. The long bake time is gentle and even, producing reliable results without constant checking.

Quick Replacement Ideas

Feta cheese — swap for goat cheese or crumbled ricotta if you prefer creamier tang.
Baby spinach — use thawed frozen spinach (well-drained) if fresh isn’t available.
Shallots — substitute 1 small yellow onion, finely chopped and cooked until soft.
Plum tomatoes — canned diced tomatoes, drained, in a pinch; discard excess liquid.
2% milk and heavy cream — for fewer calories use all 2% milk, though texture will be slightly less rich.

Equipment at a Glance

9 x 13 x 3-inch Pyrex deep baking dish — the exact size specified ensures proper thickness and bake time.
Large skillet — for sweating shallots and wilting spinach.
Large mixing bowl — to whisk eggs and dairy together.
Spatula or spoon — for pressing drained spinach and folding ingredients.
Whisk — for a smooth custard base.
Knife for testing doneness — a clean knife through the center should come out clean when done.

Watch Outs & How to Fix

Too much liquid in the casserole — press the spinach and shallots firmly after cooking to remove excess moisture. If the mix still seems watery, blot extra liquid with paper towels before folding into the eggs.
Center not set after 1 hour 20 minutes — ovens vary. Tent loosely with foil and continue baking in 10-minute intervals, checking with a knife for a clean pull.
Top browning too quickly — cover the dish lightly with foil for the remainder of the bake to prevent over-browning while the center finishes.
Bland flavor — feta and kosher salt are doing most of the seasoning. Taste the beaten egg mixture lightly before baking and adjust salt or pepper if needed.

Make It Diet-Friendly

Want to lower calories or fat? These swaps keep structure and flavor while trimming richness.

Use all 2% milk in place of the 2% milk plus heavy cream to reduce fat while keeping moisture.
Replace whole eggs with a mix of whole eggs and egg whites for lower cholesterol—remember this changes texture slightly.
Reduce feta to 8 ounces for less sodium, and add a squeeze of lemon or extra scallions to lift brightness.
For a lower-sodium version, reduce the kosher salt to 1 1/2 teaspoons and rely on black pepper and fresh herbs for flavor.

Insider Tips

Wilt the spinach in batches if your skillet is crowded. Overcrowding can steam instead of wilt and trap water.
Seed the plum tomatoes to avoid extra liquid. Cut them open and gently scoop seeds away before dicing.
Chill before slicing? If you want neat slices for a buffet, cool the casserole for 30–60 minutes to firm up further after the 10–15 minute rest.
Cut uniform pieces by using a sharp chef’s knife, wiping it between cuts to keep edges clean.
If you like a little chew and contrast, sprinkle a thin layer of additional crumbled feta on top during the last 10 minutes of baking so it browns slightly.

Storage & Reheat Guide

Cool the casserole to room temperature for no longer than two hours, then wrap tightly or transfer to an airtight container. It will keep in the refrigerator for up to 4 days. For longer storage, freeze individual slices in single layers on a sheet tray; once frozen, stack with parchment between slices and store in a zip-top bag for up to 2 months.

To reheat: thaw frozen slices overnight in the fridge. Warm a single slice in the microwave for 60–90 seconds on high, or reheat in a 350°F oven at 10–15 minutes covered with foil until heated through. For a crisp top, remove foil the last 5 minutes of reheating.

Frequently Asked Questions

Can I make this ahead? Yes. Bake it fully, let it cool, then refrigerate and reheat as needed. Alternatively, assemble and refrigerate (unbaked) up to 24 hours before baking—add a little extra bake time if chilled straight from the fridge.
What about substituting other greens? Kale or chard work, but cook them longer until tender and press out more liquid—both hold more water than baby spinach.
Is the long bake time necessary? The low-and-slow bake ensures the dense egg mixture sets evenly without becoming dry. Shortening time may leave the center unset.
My casserole sank in the middle—why? Likely underbaked in the center or opened the oven too early. Return it to the oven, check with a knife, and bake until set.

See You at the Table

This Healthy Breakfast Casserole with Spinach and Feta is the kind of recipe that rewards preparation and lends itself to small improvements over time—more scallions, less salt, extra tomatoes, or a sprinkle of herbs at the end. It’s dependable, feeds a crowd, and makes busy mornings easier without sacrificing flavor.

Try it as written once, then tweak one element at a time. Keep notes: the next time you host or prep for a week, you’ll know what to change and what to leave alone. I’ll be slicing mine thick for Sunday brunch—see you at the table.

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