Step 1

Preheat the oven to 375°F.

Step 2

Spray a 9x13-inch baking dish with nonstick cooking spray. Set aside.

Step 3

Cut the zucchini into 3/4-inch pieces. Finely chop the onion. Mince the garlic.

Step 4

Set a large pot over medium-high heat and add the butter. Once butter is melted, add the onions and zucchini. Saute until onions are softened and zucchini is slightly tender, 5-6 minutes. Add the garlic and thyme leaves and cook until fragrant, about 1 minute.

Step 5

Sprinkle the flour over zucchini and onions and stir to coat. Slowly pour the broth into the pot, stirring vigorously to dissolve flour. Pour in the half-and-half and season with the salt and black pepper.

Step 6

Cook the sauce, stirring constantly, until it begins to bubble and thicken, 3-4 minutes. Remove pot from heat.

Step 7

Add the shredded cheese to sauce and stir until melted. Add the cooked rice and fold until thoroughly coated in sauce and the zucchini is well distributed.

Step 8

Pour the zucchini and rice mixture into the prepared baking dish. Sprinkle evenly with the shredded cheese.

Step 9

Bake the casserole on middle rack of oven until bubbling at edges and cheese is golden brown on top, 30-35 minutes.

Step 10

Check to see that casserole is done. Remove from oven or add time as needed.

Step 11

Allow the casserole to rest for 10-15 minutes before serving.