Preheat the air fryer: Set to 390–400°F (200–205°C) for 3–5 minutes. A hot basket helps the veggies and sausage sear fast.
Prep the produce: Cut peppers, onion, and zucchini into even pieces so they cook at the same rate.
If using baby potatoes, halve or quarter them to about 3/4-inch pieces.
Season: In a large bowl, combine sausage and veggies. Drizzle with olive oil and sprinkle with garlic powder, smoked paprika, oregano, salt, pepper, and red pepper flakes if using. Toss until everything is well coated.
Potatoes first (if using): If you added potatoes, air fry them alone for 8 minutes to give them a head start.
Then add the remaining veggies and sausage.
Air fry in a single layer: Add the mixture to the basket in a mostly single layer. Cook for 12–15 minutes, shaking the basket halfway. Aim for caramelized edges and tender-crisp veggies.
Sausage should be browned and heated through.
Finish: Squeeze fresh lemon over the top and sprinkle with parsley. Taste and adjust salt and pepper.
Serve: Enjoy as-is, or pair with rice, quinoa, cauliflower rice, or warm crusty bread.