01 - Preheat oven to 400°F. Lightly grease a large baking dish or sheet pan.
02 - In a large bowl, combine halved potatoes and red onion with olive oil, lemon zest and juice, garlic, oregano, black pepper, chili flakes, and salt. Toss until evenly coated.
03 - Spread potato mixture evenly in prepared baking dish.
04 - Scatter feta cubes over potatoes.
05 - Bake for 35–40 minutes, stirring once halfway through, until potatoes are tender and golden brown with slightly browned feta.
06 - Remove from oven, sprinkle with fresh parsley, and serve warm.