I first threw this casserole together on a rainy Thursday when the fridge looked like a science experiment and the pantry was down to half-bags of rice, a dusty can of tomatoes, and a mountain of zucchini from my neighbor’s garden. I was tired, the kids were starving, and I needed dinner on the table in under an hour. What emerged from the oven—bubbling, golden, and aromatic—was so good that my pickiest eater asked for seconds and then thirds. Since that night, this Cheesy Zucchini Casserole has become our family’s go-to “clean-out” dish. It’s forgiving, adaptable, and somehow always tastes like you planned it weeks in advance. Whether you’re staring down end-of-summer squash or just trying to rotate the pantry before vacation, this recipe will save dinner and your grocery budget.

Why This Recipe Works

One-bowl mixing: No fancy equipment—just grate, stir, bake.
Pantry heroes: Uses canned tomatoes, dried herbs, and rice you already have.
Vegetable magnet: Zucchini shrinks while it bakes, so even veggie-skeptics polish it off.
Cheese strategy: A triple-cheese blend gives both flavor and a crusty top.
Make-ahead magic: Assemble in the morning, slide into the oven when you get home.
Freezer friendly: Bake, cool, freeze in squares for up to three months.

Ingredients You'll Need

Zucchini – Look for small to medium squash; they’re less watery and have fewer seeds. If yours are baseball-bat size, scoop out the spongy core before grating.

Long-grain white rice – The pantry workhorse. Brown rice works too, but add 10 extra minutes to the simmer time and an extra splash of broth.

Canned diced tomatoes – Fire-roasted if you have them; regular if you don’t. Drain lightly so the casserole doesn’t swim.

Onion & garlic – Non-negotiable aromatics. Yellow, white, or even a lonely shallot hanging out in the back of the drawer—use what you’ve got.

Cheese trio – Sharp cheddar for backbone, mozzarella for stretch, and a dusting of Parmesan for salty crunch. Pre-shredded is fine, but freshly grated melts silkier.

Italian seasoning – A teaspoon from that jar you bought for pizza in 2019. (No judgment—it’s still good.)

Olive oil – Just a tablespoon to slick the skillet. Butter works if your olive bottle is echo-empty.

Optional sparkle: A pinch of chili flakes, a handful of olives, or the last inch of tomato paste squeezed from the tube—clean-out cooking is about creativity.

How to Make Cheesy Zucchini Casserole for a Pantry Clean-Out Side

Prep & Preheat

Position rack in center of oven; preheat to 400 °F (204 °C). Lightly grease a 2-quart baking dish or a 10-inch oven-safe skillet. If your dish is smaller, expect a thicker casserole and add 5 minutes bake time.

Cook the Rice

In a small saucepan combine ½ cup dry rice with 1 cup water and a pinch of salt. Bring to a boil, reduce to low, cover and simmer 12 min (or per package). Remove from heat; fluff with fork. You should have about 1 ½ cups cooked.

Sauté Aromatics

While rice cooks, warm 1 Tbsp olive oil in a wide skillet over medium. Add ½ cup finely chopped onion; cook 3 min until translucent. Stir in 2 minced garlic cloves for 30 sec—just until fragrant. Remove from heat and cool slightly.

Grate & Squeeze Zucchini

Coarsely grate 4 medium zucchini (about 1 ½ lb). Wrap in a clean kitchen towel; twist and squeeze over sink to remove excess liquid. You want roughly 3 packed cups post-squeeze—this prevents a soggy casserole.

Mix the Base

In a large bowl whisk 2 eggs, ½ tsp Italian seasoning, ¾ tsp salt, ¼ tsp pepper, and a pinch of chili flakes if using. Fold in cooked rice, sautéed onion mixture, zucchini, and one cup of the canned diced tomatoes (drained). Stir until everything is coated in eggy goodness.

Cheese It Up

Add 1 cup shredded sharp cheddar and ½ cup shredded mozzarella to the bowl. Reserve remaining ½ cup cheddar for topping. Stir just until combined; over-mixing can toughen eggs.

Transfer & Top

Scrape mixture into prepared dish and press gently to level. Sprinkle reserved ½ cup cheddar plus ¼ cup grated Parmesan over surface for a lacy, golden crust.

Bake to Perfection

Bake 25–30 min until edges bubble and top is freckled brown. Broil 1–2 min for extra crunch, watching like a hawk. Let stand 10 min before slicing; this sets the custard and makes serving tidy.

Serve & Jazz Up

Cut into wedges or squares. Garnish with chopped parsley, thinly sliced scallions, or a drizzle of sriracha mayo. Leftovers reheat like a dream in a toaster oven.

Expert Tips

De-water Like a Pro

Save the zucchini liquid for soups or bread dough—there’s flavor in there!

Skillet Shortcut

If your skillet is oven-safe, mix everything right in it to save a dish.

Crust Insurance

Sprinkle a few panko mixed with oil on top for extra crunch.

Make-Ahead

Assemble through Step 7, cover, chill up to 24 hrs. Add 5–7 min bake time from cold.

Freeze Smart

Bake, cool, slice, wrap individual squares. Microwave 2 min from frozen.

Double Batch

Double the recipe and bake in a 9×13 pan for potlucks—add 10 min.

Variations to Try

Storage Tips

Refrigerator: Cool completely, cover tightly, and refrigerate up to 5 days. Reheat single servings in microwave 60–90 sec or in toaster oven 8 min at 350 °F.

Freezer: Wrap cooled squares in plastic wrap, then foil; freeze up to 3 months. Thaw overnight in fridge or microwave from frozen.

Make-Ahead: Assemble (unbaked), cover with plastic and then foil; freeze up to 2 months. Bake from frozen 55–60 min at 375 °F, adding foil if top browns too quickly.

Frequently Asked Questions

Absolutely. Yellow squash has similar moisture content and flavor. A mix of zucchini and yellow squash looks gorgeous too.

Most likely the zucchini wasn’t squeezed enough or tomatoes weren’t drained. Next time wring out zucchini until the towel barely drips.

Yes—halve everything and bake in an 8-inch square dish for 20–22 min.

Yes, raw rice won’t finish cooking in the oven. Leftover take-out rice is perfect.

Serve alongside grilled chicken, a crisp green salad, or even a fried egg for brunch.

The center should feel set when you gently jiggle the pan, and the cheese should be freckled golden.