Preheat your oven to 375°F and lightly grease a small oven-safe baking dish with a touch of oil.
In a skillet over medium heat, add the olive oil along with the ground turkey sausage, diced onion, and red bell pepper.
Sauté the mixture, breaking up the sausage with a spatula, until the meat is browned and the vegetables are softened.
Stir in the baby spinach and cook for 1 minute until it just begins to wilt, then remove the skillet from the heat.
In a medium mixing bowl, whisk together the eggs, egg whites, sea salt, black pepper, and garlic powder until well combined.
Spread the sausage and vegetable mixture evenly into the prepared baking dish.
Pour the egg mixture over the sausage and vegetables, then sprinkle the crumbled feta cheese on top.
Bake for 20 to 25 minutes, or until the eggs are completely set in the center and the top is lightly golden.