Preheat the oven to 350°F (175°C).

Peel and chop sweet potatoes into 1-inch cubes; dice onions and green peppers, and mince garlic.

Grease a 9x13-inch casserole dish.

In a large saucepan, sauté onion and green pepper in oil for 4-5 minutes; add sweet potatoes for 8-9 minutes, then add minced garlic for 1 minute.

Pour sautéed vegetables into the greased casserole dish.

Cook turkey sausage in the same saucepan until browned, about 5-7 minutes; drain excess liquid.

Combine turkey sausage with the sautéed vegetables in the casserole dish.

In a mixing bowl, whisk together eggs, milk, thyme, salt, pepper, and cheese until smooth.

Pour the egg mixture over the vegetable and sausage blend, and gently stir to combine.

Bake in the preheated oven for 40-45 minutes until the center is set.

Let the casserole rest for 5-10 minutes before serving.