01 - Preheat your oven to 375°F (190°C).
02 - Heat olive oil in a 10-inch ovenproof non-stick skillet over medium heat. Add diced bell pepper and zucchini; sauté for 3 to 4 minutes until slightly softened.
03 - Add sliced green onions and halved cherry tomatoes; cook for another 2 minutes.
04 - Stir in chopped baby spinach and cook until just wilted, approximately 1 minute.
05 - In a mixing bowl, whisk together eggs, skim milk, salt, black pepper, dried oregano, and chili flakes if using.
06 - Pour the egg mixture evenly over the sautéed vegetables in the skillet.
07 - Sprinkle crumbled reduced-fat feta cheese evenly over the top of the eggs and vegetables.
08 - Cook the mixture on the stovetop over medium heat for 2 to 3 minutes until the edges begin to set.
09 - Transfer the skillet to the preheated oven and bake for 10 to 12 minutes or until the center is firm and lightly golden.
10 - Allow the dish to cool slightly, then slice and serve warm or at room temperature.