Preheat your oven to 375°F (190°C) and lightly grease a small oven-safe baking dish with a touch of oil.
Heat the extra virgin olive oil in a non-stick skillet over medium heat.
Add the diced yellow onion and red bell pepper to the skillet, sautéing for 3-4 minutes until the vegetables are tender and fragrant.
Stir in the sliced chicken sausage and cook for another 3 minutes until the edges are lightly browned.
Add the fresh spinach to the skillet and toss continuously until just wilted, then remove the pan from the heat.
In a medium mixing bowl, whisk together the whole eggs, egg whites, sea salt, black pepper, and garlic powder until well combined and slightly frothy.
Transfer the cooked sausage and vegetable mixture into the prepared baking dish, spreading it out into an even layer.
Pour the egg mixture over the vegetables and sausage, ensuring the liquid is distributed evenly.
Bake for 20-25 minutes, or until the eggs are completely set in the center and the top is slightly golden.
Let the bake rest for 5 minutes before slicing into portions and serving warm.