Preheat oven to 375°F and lightly grease a small oven-safe baking dish.
Heat olive oil in a skillet over medium heat and sauté the diced onion and minced garlic until fragrant and translucent.
Add the ground turkey to the skillet and cook until browned and crumbled, ensuring it is fully cooked through.
Stir in the fresh baby spinach and cook for 1-2 minutes until just wilted, then remove the pan from heat to cool slightly.
In a medium bowl, whisk together the large eggs, liquid egg whites, sea salt, black pepper, and dried oregano.
Gently fold the cooked turkey and spinach mixture along with the crumbled feta cheese into the egg mixture.
Lay the phyllo dough sheet into the prepared baking dish, allowing the edges to drape over the sides.
Pour the turkey and egg filling into the center and fold the overhanging phyllo edges back over the top to partially cover.
Bake for 25 to 30 minutes or until the egg filling is set and the phyllo pastry is beautifully golden and crisp.