01 - Set the air fryer to 350°F and allow it to fully preheat while you prepare the ingredients.
02 - In a mixing bowl, combine the sliced red bell pepper, zucchini, red onion, cherry tomatoes, Kalamata olives, garlic, chopped parsley, and dried oregano. Drizzle with half of the olive oil and all of the lemon juice, then season with salt and pepper. Toss everything together until the vegetables are evenly coated.
03 - Cut 4 large sheets of parchment paper, approximately 12x16 inches each, large enough to fully enclose each fillet and its topping.
04 - Place one cod fillet in the center of each parchment sheet. Season each fillet lightly with salt and pepper on both sides.
05 - Divide the seasoned vegetable mixture evenly among the four fillets, mounding it on top of each one. Arrange 2 to 3 thin lemon slices over the vegetables on each packet. Drizzle the remaining olive oil over the tops.
06 - Fold the parchment paper over each fillet and vegetable stack. Crimp and fold the edges tightly together to form sealed packets, enclosing the fish and vegetables completely in the style of en papillote.
07 - Place the sealed parchment packets into the air fryer basket, working in batches if they do not all fit in a single layer. Cook at 350°F for 13 to 15 minutes, until the cod is opaque throughout and flakes easily when pierced with a fork.
08 - Carefully open each parchment packet, watching for the hot steam. Serve immediately, either directly in the parchment for a rustic presentation or transferred to individual plates.