Preheat your oven to 375°F (190°C) and lightly grease a small oven-safe baking dish with the olive oil.
In a skillet over medium heat, cook the ground turkey sausage until browned and fully cooked, breaking it into small crumbles with a spatula.
Add the diced red bell pepper and spinach to the skillet, sautéing for 3-4 minutes until the peppers are tender and the spinach has wilted.
In a medium mixing bowl, whisk together the whole eggs, egg whites, sea salt, black pepper, and garlic powder until the mixture is well combined and slightly frothy.
Spread the cooked sausage and vegetable mixture evenly across the bottom of the prepared baking dish.
Pour the egg mixture over the sausage and vegetables, then sprinkle the crumbled feta cheese evenly on top.
Bake for 20-25 minutes, or until the eggs are set in the center and the edges are lightly golden brown.