Preheat your oven to 350°F (175°C). Gather and prepare your ingredients.

Chop your sweet potatoes, onion, and green pepper into 1-inch pieces.

In a large skillet, heat avocado oil over medium heat. Add sweet potatoes, onion, and green pepper, and sauté for 8 to 9 minutes. Add minced garlic in the final minute.

Transfer the sautéed vegetables into a greased 9x13-inch casserole dish. If using turkey sausage, cook it separately until browned, then mix it with the veggies.

In a separate bowl, whisk eggs with milk, thyme, salt, and pepper until smooth. Add shredded cheese to this mixture.

Pour the egg mixture over the cooked vegetables and sausage in the casserole dish. Stir gently to combine.

Bake in the preheated oven for 40 to 45 minutes until firm in the center and golden brown on top.

Allow the casserole to cool for 5 to 10 minutes before serving.