01 - Set oven temperature to 375°F and allow to fully preheat.
02 - Drizzle 1 tablespoon olive oil into a medium oven-safe skillet or baking dish. Add baby spinach, cherry tomatoes, red onion, and garlic. Season lightly with salt and black pepper, then toss until evenly coated.
03 - Scatter crumbled feta evenly over the vegetable mixture.
04 - Drizzle the remaining olive oil over top and sprinkle with dried oregano and chili flakes if desired.
05 - Create four small wells in the mixture. Carefully crack one egg into each well, spacing evenly apart.
06 - Transfer skillet or dish to oven and bake for 15 to 20 minutes, or until egg whites are just set while the yolks remain slightly runny.
07 - Remove from oven and let rest briefly before serving warm.