Baked Zucchini Spinach Feta Casserole

The first time I made this casserole, I was trying to use up an abundance of zucchini from my garden and a block of feta that had been sitting in my fridge. My husband took one bite and asked why I'd never made it before, which is honestly the best kind of cooking surprise when you're just throwing things together.

Last summer, my neighbor dropped off more zucchini than any human should reasonably consume, and this casserole saved me from zucchini fatigue for weeks. Even my kids who claim to hate vegetables came back for seconds, which still feels like a personal victory.

Ingredients

• 2 medium zucchinis: Slice them uniformly so they cook evenly, about 1/4 inch thick works perfectly
• 5 oz fresh baby spinach: The stems are tender enough that you dont need to remove them, saves so much time
• 1 small onion: Finely chopped so it disperses throughout rather than creating big onion pockets
• 2 garlic cloves: Minced fresh, never powdered, the difference is worth the extra minute
• 6 oz feta cheese: Crumble it yourself rather than buying pre crumbled, the texture is so much better
• 1 cup mozzarella cheese: Grated from a block if you can manage it, melts more evenly
• 4 large eggs: Room temperature eggs incorporate more smoothly into the milk mixture
• 3/4 cup milk: Whole milk gives you that creamy custard like texture we want
• 2 tbsp extra virgin olive oil: Divided use, one for cooking the aromatics and one for drizzling on top
• 1/2 tsp dried oregano: Rub it between your fingers before adding to wake up the oils
• 1/4 tsp ground black pepper: Freshly cracked adds way more flavor than pre ground
• 1/4 tsp salt: Feta is already salty, so taste before adding more
• 1/4 tsp crushed red pepper flakes: Optional but that little hit of heat makes everything pop
• 1 tbsp butter or olive oil: For greasing the dish, butter gives better browning but olive oil works too

Instructions

Get your oven ready:

Preheat to 375°F and grease your 9x9 inch baking dish with butter or olive oil, making sure to get into the corners

Start the aromatics:

Heat 1 tablespoon olive oil in a large skillet over medium heat, add chopped onion and sauté for 3 minutes until translucent, then add garlic and cook for just 1 minute

Wilt the spinach:

Add spinach to the skillet and stir constantly for about 2 minutes until it collapses into itself, then remove from heat and let it cool slightly so it doesnt cook the eggs when you mix them

Make the custard:

In a large bowl, whisk together eggs, milk, oregano, black pepper, and salt until everything is completely blended and frothy

Layer like a pro:

Arrange half the zucchini slices in your prepared dish, spread half the spinach mixture on top, then sprinkle with half the feta and mozzarella

Do it again:

Repeat with remaining zucchini, spinach, feta, and mozzarella, building those beautiful layers that will make it look impressive when you serve it

Pour and finish:

Pour the egg mixture evenly over everything, drizzle with remaining olive oil, and sprinkle red pepper flakes on top if you like that gentle heat

Bake until golden:

Bake uncovered for 35 minutes until the casserole is set in the center and the top has those gorgeous browned cheese pockets

The hardest part:

Let it rest for 10 minutes before slicing, this is crucial or it will ooze everywhere, but I promise its worth the wait

Save

My mom asked for this recipe after I served it at Easter brunch, and now she makes it more often than I do. Theres something about that combination of vegetables and cheese that feels like comfort food but still light enough for spring weather.

Make It Your Own

Sometimes I add chopped fresh dill or parsley right before baking, especially if I have them wilting in my herb garden. The fresh herbs add this bright pop that cuts through all that rich cheese.

Cheese Swaps

Ive used Gruyère instead of mozzarella when I was feeling fancy, and Monterey Jack works beautifully too. The key is keeping that contrast between the tangy feta and something more mild and melty.

Serving Ideas

A crisp green salad with a lemon vinaigrette cuts right through the richness. I also love it with some crusty bread to soak up any juices that escape.

• Great for meal prep and actually tastes better the next day
• Freezes beautifully for up to three months if you wrap it tightly
• Works for breakfast, lunch, or dinner which I find incredibly convenient

Save

This recipe has become my go to for new moms and anyone who needs a meal they can just heat and eat. Its nourishing without being heavy, which is exactly what I want when feeding people I care about.

Recipe FAQ

→ Can I prepare this casserole ahead of time?

Yes, assemble the casserole up to 24 hours in advance and refrigerate. Add 5-10 minutes to baking time if baking cold from the refrigerator.

→ Can I freeze this dish?

The casserole freezes well for up to 3 months. Wrap tightly in foil and plastic wrap. Thaw overnight in the refrigerator before reheating at 350°F until heated through.

→ What can I substitute for feta cheese?

Goat cheese, ricotta salata, or halloumi work well as alternatives. For a dairy-free option, try a firm tofu seasoned with lemon juice and herbs.

→ How do I know when it's done baking?

The casserole is ready when the top is golden brown, the edges are bubbling, and a knife inserted in the center comes out clean. The center should be set, not jiggly.

→ Can I add other vegetables?

Yes, bell peppers, mushrooms, or artichoke hearts complement the flavors well. Just be sure to sauté them with the onions to remove excess moisture before layering.