01 - Preheat the oven to 400°F. Lightly grease a large baking dish or sheet pan with olive oil or cooking spray.
02 - In a large bowl, combine halved potatoes, red onion wedges, olive oil, lemon zest, lemon juice, minced garlic, dried oregano, black pepper, chili flakes, and salt. Toss thoroughly until all vegetables are evenly coated.
03 - Spread the seasoned potato mixture evenly across the prepared baking dish, ensuring vegetables are in a single layer for proper roasting.
04 - Scatter the feta cheese cubes over the top of the potato mixture, distributing them evenly throughout the dish.
05 - Bake for 35-40 minutes, stirring the potatoes once halfway through cooking. Continue until potatoes are tender when pierced with a fork, golden brown, and the feta has softened and slightly browned on the edges.
06 - Remove from the oven and immediately sprinkle with fresh chopped parsley. Serve warm while the feta is still creamy and the potatoes are at their peak flavor.