Preheat your oven to 375°F and lightly grease six wells of a standard muffin tin with a touch of olive oil.
In a small skillet over medium heat, add the teaspoon of olive oil and the ground turkey, sautéing until browned and cooked through.
Add the diced red bell pepper and yellow onion to the skillet, cooking for 3 to 4 minutes until the vegetables are tender and aromatic.
Stir in the chopped baby spinach until just wilted, then remove the pan from the heat to cool slightly.
In a medium mixing bowl, whisk together the whole eggs, egg whites, sea salt, black pepper, and garlic powder until the mixture is uniform.
Distribute the turkey and vegetable mixture evenly among the six prepared muffin cups.
Pour the egg mixture over the fillings until each cup is nearly full, then sprinkle the crumbled feta cheese over the top of each.
Bake for 18 to 20 minutes, or until the egg cups have risen and the tops are a beautiful golden brown.