Preheat your oven to 375°F (190°C) and lightly grease a small oven-safe baking dish with a touch of olive oil.
Place a non-stick skillet over medium-high heat with 0.5 tsp of olive oil. Add the diced yellow onion and ground turkey sausage, breaking the meat apart with a spatula until browned and cooked through.
Add the fresh baby spinach to the skillet and sauté for 1-2 minutes until just wilted, then remove from heat.
In a medium mixing bowl, whisk together the egg whites, whole egg, sea salt, black pepper, garlic powder, and dried oregano until well combined and slightly frothy.
Spread the sausage and spinach mixture evenly across the bottom of the prepared baking dish.
Pour the egg mixture over the sausage and vegetables, ensuring everything is evenly submerged.
Bake for 20-25 minutes, or until the eggs are set in the center and the edges are lightly golden brown.
Allow the bake to cool for 5 minutes before slicing and serving. This can be stored in the refrigerator for up to 4 days for easy meal prep.