01 - Preheat oven to 375°F.
02 - Heat olive oil in a 10-inch oven-safe skillet over medium heat. Add onion and bell pepper, sauté for 3–4 minutes until softened.
03 - Stir in garlic and cook for 1 minute. Add spinach and cook for 1–2 minutes until wilted.
04 - Add cooked lentils to the skillet and mix until evenly combined with vegetables.
05 - In a large bowl, whisk together eggs, milk, oregano, salt, and pepper. Stir in half the chopped parsley.
06 - Pour egg mixture evenly over vegetables and lentils in skillet. Gently shake to distribute. Sprinkle crumbled feta on top.
07 - Cook over low heat for 2–3 minutes until edges begin to set.
08 - Transfer skillet to oven and bake for 12–15 minutes until center is set and top is lightly golden.
09 - Remove from oven, let cool slightly. Garnish with remaining parsley. Slice into wedges and serve warm or at room temperature.