Arrange cod on a sheet pan and toss diced peppers and onions with canned tomatoes, olives, garlic, oregano, and olive oil in a bowl.
Pour tomato mixture around the cod, season everything with salt and pepper.
Bake at 400°F for 15 minutes until fish flakes easily and vegetables are tender.
Serve the cod with its sauce spooned over the top.
Photo: Ioannis Sarantis / Unsplash