Preheat oven to 350°F (175°C) and lightly grease six slots of a standard muffin tin with cooking spray or a touch of olive oil.
Heat the olive oil in a medium skillet over medium-high heat and add the ground turkey, diced red onion, and red bell pepper.
Sauté the mixture for 5-7 minutes until the turkey is fully browned and the vegetables have softened.
Add the baby spinach to the skillet and stir for 1 minute until just wilted, then remove the pan from heat.
In a large mixing bowl, whisk together the whole eggs, liquid egg whites, sea salt, black pepper, dried oregano, and red pepper flakes until well combined.
Evenly distribute the turkey and vegetable mixture into the prepared muffin cups, filling each about two-thirds full.
Pour the egg mixture over the turkey and vegetables in each cup, leaving a small amount of space at the top.
Bake for 20 to 25 minutes or until the egg cups are set in the center and slightly golden on the edges.