Cheesy Zucchini Corn Casserole in the Crockpot

This sweet corn and zucchini parmesan casserole is the kind of dish that feels like summer in a bowl. Diced zucchini and sweet corn are tossed with garlic herb butter, two kinds of melty Italian cheese, eggs, and cream, then left to bubble away in a slow cooker until puffed and golden.

The result is a savory, custardy side or vegetarian main that pairs with almost anything. It is a true dump-and-go recipe: no sautéing, no boiling, no fuss.

When summer zucchini and sweet corn are at their peak, this slow cooker casserole is the easiest way to turn them into something special. The vegetables stay tender but not mushy, while the eggs and cream create a soft, custard-like base that puffs as it cooks. Provolone brings a gentle, nutty melt, and parmesan adds a salty, savory finish.

Because everything goes into the Crockpot at once, there is minimal prep and no oven heat to battle on a warm day. The slow cooker also keeps the casserole warm for serving, making it a practical choice for potlucks, weeknight dinners, or holiday sides. This recipe is flexible, forgiving, and endlessly adaptable to what is in the fridge.

Ingredients

Why this recipe works

The slow cooker provides gentle, even heat that cooks the eggs and cream into a soft, set custard without the risk of curdling or overcooking that can happen on the stovetop.

Because the heat is low and moist, the zucchini and corn cook through evenly, releasing just enough liquid to keep the casserole creamy without becoming watery. The lid traps steam, which helps the top puff slightly while the edges turn golden and caramelized.

Combining the vegetables with cheese, eggs, and cream creates a cohesive mixture that holds together when scooped, yet stays tender and moist. The eggs act as a binder, the cream adds richness, and the cheeses melt into every crevice, creating pockets of gooey goodness. This method is nearly foolproof: as long as the eggs reach 160°F (71°C), the casserole is safe and perfectly set.

Notes and substitutions

Use fresh zucchini if possible, but frozen and thawed zucchini works too — just drain it well to avoid excess water. Sweet corn can be fresh, frozen, or canned; if using canned, drain it thoroughly.

Garlic herb butter adds flavor without extra steps, but plain butter with a pinch of garlic powder and dried herbs is an easy substitute. Provolone is mild and melts beautifully; mozzarella or fontina are good stand-ins. Parmesan should be freshly grated for the best flavor and melting.

A 6-quart slow cooker is ideal for this recipe, but a 4-quart will also work if the ingredients fit. The casserole can be assembled the night before and refrigerated, then cooked the next day — just add 15 to 20 minutes to the cooking time. Leftovers can be reheated in the microwave or in a skillet. This dish is vegetarian, but it is not vegan or dairy-free due to the cheese, cream, and butter.

• garlic herb butter: Use 4 tbsp salted butter melted with 1/2 tsp garlic powder and 1 tsp dried Italian herbs.
• provolone: Substitute with shredded mozzarella or fontina for an equally melty, mild cheese.
• heavy cream: Half-and-half works, though the casserole will be slightly less rich.
• fresh basil: Omit the basil or use 1 tsp dried basil mixed into the casserole before cooking.

Equipment

• 6-quart slow cooker
• Mixing spoon
• Measuring cups and spoons
• Chef's knife
• Cutting board