Cheesy Baked Zucchini Casserole

Prep Time: 20 minutes (plus 20 minutes for draining)
Cook Time: 35 minutes
Total Time: 1 hour 15 minutes
Servings: 6 to 8 servings
Culinary Intensity / Difficulty: Low to Moderate (Beginner-friendly)

Thermal Intensities & Timing Guide

Phase	Duration	Temperature / Intensity	Primary Purpose
Vegetable Prep	20 min	Room Temperature	Draw out excess moisture with salt to prevent a watery base.
Sauce Reduction	4–5 min	Medium-Low Heat	Melt cheeses and build an emulsified, garlic-cream base.
Primary Bake	25 min	$400^\circ\text{F}$ ( $204^\circ\text{C}$ )	Cook zucchini through until tender and heat the casserole until bubbly.
Topping Crisp	8–10 min	$400^\circ\text{F}$ ( $204^\circ\text{C}$ )	Brown the buttered breadcrumbs to achieve a golden, crunchy crust.
Resting Period	10 min	Ambient / Countertop	Allow the cheese sauce to set for clean slicing and serving.

Ingredients

For the Vegetable Base:

$2.5\text{ lbs}$ Medium Zucchini (approx. 4–5 zucchini), sliced into $\frac{1}{4}$ -inch rounds
$1\text{ tsp}$ Sea Salt (for draining)
$1\text{ tbsp}$ Extra-Virgin Olive Oil
$1\text{ small}$ Yellow Onion, finely diced
$3\text{ cloves}$ Garlic, minced

For the Cheese & Binder Mixture:

$1.5\text{ cups}$ Shredded Sharp Cheddar or Gruyère Cheese (divided)
$\frac{1}{2}\text{ cup}$ Grated Parmesan Cheese
$\frac{1}{2}\text{ cup}$ Heavy Cream (or sour cream/full-fat Greek yogurt)
$2\text{ large}$ Eggs, lightly beaten
$1\text{ tsp}$ Italian Seasoning
$\frac{1}{2}\text{ tsp}$ Garlic Powder
$\frac{1}{4}\text{ tsp}$ Black Pepper
$\frac{1}{8}\text{ tsp}$ Red Pepper Flakes (optional, for mild heat)

For the Golden Breadcrumb Topping:

$\frac{3}{4}\text{ cup}$ Panko Breadcrumbs
$2\text{ tbsp}$ Unsalted Butter, melted
$\frac{1}{4}\text{ cup}$ Reserved Parmesan Cheese

1.Drain and Dry the Zucchini:Crucial for preventing a watery casserole.

Slice the zucchini into uniform $\frac{1}{4}$ -inch rounds. Place them in a large colander over a sink, sprinkle with $1\text{ tsp}$ sea salt, and toss to coat evenly. Let stand for 20 minutes. The salt will draw out excess moisture through osmosis. After 20 minutes, thoroughly pat the rounds dry using clean kitchen towels or heavy-duty paper towels.

2.Sauté Aromatics:Medium Heat (approx. 5 minutes).

Heat $1\text{ tbsp}$ olive oil in a skillet over medium heat. Add the diced yellow onion and sauté for 3 to 4 minutes until translucent and soft. Add the minced garlic and cook for another 60 seconds until fragrant, taking care not to burn the garlic. Remove from heat and set aside to cool slightly.

3.Whisk the Cheese Sauce:Low to Medium-Low Heat.

In a medium bowl, whisk together the heavy cream, beaten eggs, garlic powder, Italian seasoning, black pepper, red pepper flakes, sautéed onions/garlic, $\frac{1}{4}\text{ cup}$ of Parmesan, and $1\text{ cup}$ of the shredded cheddar or Gruyère cheese.

4.Assemble the Casserole:

Preheat your oven to $400^\circ\text{F}$ ( $204^\circ\text{C}$ ). Lightly grease a 9×13-inch baking dish (or an 8×11-inch dish) with cooking spray or butter. Layer the patted-dry zucchini slices evenly along the bottom. Pour the cheese mixture evenly over the top, gently shaking the dish to allow the sauce to settle into the crevices. Sprinkle the remaining $\frac{1}{2}\text{ cup}$ of shredded cheese across the top.

5.Bake Uncovered:400°F (204°C) for 25 minutes.

Place the casserole dish on the center rack of the preheated oven. Bake uncovered for 25 minutes until the zucchini becomes tender and the cheese sauce begins to bubble gently around the edges.

6.Add Topping and Finish:400°F (204°C) for 8-10 minutes.

While the casserole bakes, combine the Panko breadcrumbs, melted butter, and the remaining $\frac{1}{4}\text{ cup}$ of Parmesan cheese in a small bowl. Carefully remove the casserole from the oven, sprinkle the buttered breadcrumbs evenly over the top, and return it to the oven for 8 to 10 minutes, or until the crumb topping turns deep golden-brown and crunchy.

7.Rest and Serve:

Remove the casserole from the oven. Let it rest at room temperature for 10 minutes before serving. This resting period is critical—it allows the hot cheeses and egg binder to set properly, making slicing much easier. Garnish with fresh parsley if desired.

Recipe Variations

Low-Carb / Keto Adaptation: Omit the Panko breadcrumbs completely. Replace the topping with a combination of extra Parmesan cheese, crushed pork rinds, and almond flour for a high-protein, zero-grain crunch.
Protein Boost: Stir $1\text{ cup}$ of cooked, crumbled Italian sausage or diced grilled chicken breast into the cheese mixture before baking.
Mixed Summer Squash: Substitute half of the green zucchini with yellow summer squash to create a visual presentation.

Nutritional Information

Estimates per serving (based on 8 equal portions using standard whole milk/heavy cream and full-fat cheddar):

Calories: $245\text{ kcal}$
Total Fat: $18\text{ g}$
- Saturated Fat: $10\text{ g}$
- Trans Fat: $0\text{ g}$
Cholesterol: $85\text{ mg}$
Sodium: $480\text{ mg}$
Total Carbohydrates: $9\text{ g}$
- Dietary Fiber: $2\text{ g}$
- Sugars: $3\text{ g}$
Net Carbohydrates: $7\text{ g}$
Protein: $12\text{ g}$
Calcium: $280\text{ mg}$ (approx. 25% Daily Value)
Vitamin D: $0.8\text{ mcg}$