Heavenly Cheesy Zucchini Casserole with 3 Cheeses

Name: Heavenly Cheesy Zucchini Casserole with 3 Cheeses
Prep time: 15 min
Cook time: 35 min
Total time: 50 min
Cuisine: American
Ingredients: 3 medium zucchinis, sliced; 1 cup shredded cheddar cheese; 1/2 cup grated Parmesan cheese; 1/2 cup breadcrumbs; 2 eggs, beaten; 1/2 cup milk; 1 small onion, diced; 2 cloves garlic, minced; 1 tbsp olive oil; 1 tsp salt; 1/2 tsp black pepper

Author: Rosa Bellini

Published: April 14, 2025

Updated: June 28, 2025

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I still remember the first time I made this cheesy zucchini casserole – it was one of those “what do I do with all this zucchini?” moments that turned into a family favorite. Now, when summer rolls around and my garden (or the farmer’s market) overflows with zucchini, this is the first recipe I reach for. It’s the kind of comfort food that feels fancy but secretly couldn’t be simpler – just layer upon layer of tender zucchini, melty cheese, and that perfect crispy topping. After making dozens of versions over the years, I’ve perfected the balance of textures and flavors that makes this dish so special. Trust me, even zucchini skeptics come back for seconds!

Cheesy Zucchini Casserole - detail 1

Why You’ll Love This Cheesy Zucchini Casserole

This casserole is one of those rare recipes that checks all the boxes – and I’m not just saying that because I’ve eaten it for lunch three days in a row (oops!). Here’s why it’s become my go-to:

Weeknight lifesaver: From chopping to serving, it’s ready in under an hour – perfect for those “what’s for dinner?” panic moments
Flavor bomb: The combo of three cheeses (yes, three!) with garlicky zucchini creates this magical savory-sweet balance
Vegetarian comfort food: Hearty enough to satisfy meat-lovers but completely veggie-packed
Crowd-pleaser: My picky nephew actually asks for seconds – and that’s saying something!

The best part? It tastes even better as leftovers (if it lasts that long).

Ingredients for Cheesy Zucchini Casserole

Here’s what you’ll need to make this glorious, bubbly casserole – I promise it’s all simple stuff you probably have already. Just measure carefully and you’re golden:

3 medium zucchinis (about 1½ lbs total), sliced into ¼-inch rounds – not too thin or they’ll disappear!
1 cup shredded cheddar cheese (packed) – I like sharp for more flavor
½ cup grated Parmesan cheese – the good stuff from the refrigerated section, not the shelf-stable kind
½ cup plain breadcrumbs – panko works great for extra crunch
2 large eggs, beaten – they’re the glue holding everything together
½ cup whole milk – 2% works in a pinch but whole gives the creamiest texture
1 small yellow onion, diced small – about ½ cup
2 cloves garlic, minced – more if you’re feeling bold!
1 tbsp olive oil – for sautéing those aromatics
1 tsp kosher salt + ½ tsp black pepper – season as you go!

Ingredient Notes & Substitutions

No stress if you need to swap things out – here’s what I’ve tested that works:

Gluten-free? Use gluten-free breadcrumbs or crushed gluten-free crackers instead.
Dairy-free? Try vegan cheddar shreds and nutritional yeast instead of Parmesan.
Out of fresh garlic? ½ tsp garlic powder works (but fresh is better!).
For extra richness, swap half the milk for heavy cream – dangerous but delicious!
Yellow squash works great alongside or instead of zucchini.

The key is keeping the ratios similar so your casserole still sets properly. Now let’s get cooking!

How to Make Cheesy Zucchini Casserole

Okay, let’s get this cheesy zucchini casserole in the oven! I promise it’s easier than it looks – just follow these simple steps and you’ll have a golden, bubbly masterpiece in no time. The key is taking it one step at a time and not rushing the process (though I know the cheesy smell will make that hard!).

Cheesy Zucchini Casserole - detail 2

Step 1: Prep the Zucchini and Aromatics

First things first – grab that zucchini and slice it into ¼-inch rounds. Too thin and they’ll turn to mush; too thick and they won’t cook through. While you’re at it, dice the onion nice and small – we want it to melt into the casserole, not stand out in big chunks. Heat the olive oil in your skillet over medium heat and toss in the onion and garlic. Cook just until they’re soft and fragrant, about 3 minutes – any longer and the garlic might burn (trust me, I’ve learned this the hard way!).

Step 2: Mix the Casserole Base

Now for the fun part! In a big bowl, toss together the zucchini slices, sautéed onion and garlic, both cheeses, breadcrumbs, eggs, milk, salt and pepper. Use your hands if you need to – it’s messy but effective! The mixture should be moist but not soupy – if it looks too wet, sprinkle in a few more breadcrumbs. Too dry? Add a splash more milk. This is where the magic starts to happen as everything comes together.

Step 3: Bake to Perfection

Pour your mixture into a greased 9×13 baking dish and pop it in your preheated 375°F oven. Now the hardest part – waiting! Bake for 30-35 minutes until the top is golden brown and the edges are bubbling like crazy. When you jiggle the pan, the center should be set but still slightly wobbly. Let it cool for at least 10 minutes before serving – I know it’s tempting to dive right in, but this helps everything set up perfectly.

Cheesy Zucchini Casserole - detail 3

Tips for the Best Cheesy Zucchini Casserole

After making this casserole more times than I can count, here are my hard-won secrets for absolute perfection:

Dry those zucchinis! After slicing, pat them dry with paper towels – extra moisture makes for a soggy casserole.
Cheese distribution matters: Reserve a handful of cheddar to sprinkle on top right before baking for that gorgeous golden crust.
Size consistency is key: Try to slice all zucchini rounds about the same thickness so they cook evenly.
The jiggle test: Your casserole is done when the edges are bubbling and the center just barely jiggles when shaken.

Oh, and always let it rest before cutting – I know it’s tempting, but those 10 minutes make all the difference!

Serving Suggestions for Cheesy Zucchini Casserole

This casserole is a total team player at the dinner table – it loves company! My favorite way to serve it is with a bright, tangy salad to cut through all that cheesy goodness. A simple arugula salad with lemon vinaigrette does the trick, or go for a classic Caesar if you’re feeling indulgent. Crusty garlic bread is non-negotiable in my house – perfect for scooping up every last cheesy bite.

For heartier meals, it pairs beautifully with grilled chicken or roasted salmon. And here’s a secret – leftovers make an amazing breakfast with a fried egg on top. Don’t knock it till you try it!

Storing and Reheating Cheesy Zucchini Casserole

Let me tell you, this casserole somehow gets even better the next day – if you have leftovers, that is! Here’s how to keep it tasting fresh:

Fridge storage: Cool completely, then cover tightly with foil or transfer to an airtight container. It’ll keep for up to 3 days (though mine never lasts that long!).
Reheating magic: For that just-baked texture, warm slices in a 350°F oven for 15 minutes. Microwave works in a pinch (about 90 seconds), but the topping won’t stay as crispy.

One warning – it never reheats quite as perfectly as day one, so don’t be shy about seconds!

Nutritional Information

Here’s the nutrition breakdown per serving (based on 6 servings), but remember – these numbers can change depending on your exact ingredients and brands. Consider this your ballpark estimate while you enjoy every cheesy bite:

Calories: 220
Protein: 12g
Carbs: 15g
Fiber: 2g
Sugar: 4g
Fat: 12g

Nutrition varies based on ingredients/brands. Values are estimates.

Common Questions About Cheesy Zucchini Casserole

I get questions about this recipe all the time – here are the answers to what everyone wants to know:

“Can I freeze cheesy zucchini casserole?”
Nope, and trust me, I’ve tried! The texture turns watery when thawed. This dish is best fresh or kept in the fridge for a couple days.

“My casserole came out watery – what went wrong?”
Ah, the zucchini strikes again! Next time, salt your sliced zucchini and let it sit for 10 minutes, then pat dry. Those little green guys hold so much water!

“Can I make this ahead?”
Absolutely! Assemble everything (except the topping) up to a day in advance. Cover and refrigerate, then add the breadcrumb topping right before baking.

“What cheese works best if I don’t have cheddar?”
I’ve used Monterey Jack, Colby, or even Gruyère in a pinch. Just avoid super soft cheeses that might make it greasy.

“Is there a way to make this lower carb?”
Try almond flour instead of breadcrumbs – it changes the texture a bit, but still gives that nice crust!

Final Thoughts

There you have it – my absolute favorite way to turn humble zucchini into something extraordinary. I’d love to hear how your cheesy zucchini casserole turns out! Snap a pic when that golden crust comes out of the oven and tag me – nothing makes me happier than seeing your kitchen creations. Now go forth and bake up some cheesy magic!