Preheat the oven: Set to 375°F (190°C). Lightly grease a 9x13-inch baking dish or use a large oven-safe skillet.
Sauté aromatics: Heat olive oil over medium heat.
Add onion with a pinch of salt and cook 4–5 minutes until soft. Stir in garlic, oregano, and red pepper flakes for 30 seconds until fragrant.
Add peppers and tomatoes: Stir in chopped roasted red peppers and the canned tomatoes with their juices. Let it simmer for 2 minutes to mingle flavors.
Combine orzo and broth: Add the dry orzo and broth.
Stir well, scraping the bottom so nothing sticks. Bring to a gentle simmer.
Wilt the greens: Fold in the spinach or kale. Cook 1–2 minutes until slightly wilted.
Season with salt and pepper.
Stir in feta and lemon: Remove from heat. Mix in the feta, lemon zest, and lemon juice. Taste and adjust salt, pepper, and chili flakes.
Top and bake: If using a skillet, spread the mixture evenly.
Sprinkle with extra feta and mozzarella/provolone, if using. Bake uncovered for 18–22 minutes until the orzo is tender and the top is lightly golden and bubbling.
Rest and garnish: Let it rest 5 minutes so the sauce settles. Finish with chopped basil or parsley and a drizzle of olive oil if you like.
Serve: Spoon into bowls.
Add a squeeze of lemon for brightness and cracked black pepper on top.