Preheat the oven to 350˚F.
Pulse the cauliflower in a food processor into rice-like grains.
Heat the oil in a skillet over medium heat then add the cauliflower – cook for 6 to 8 minutes until tender.
Spoon the cauliflower rice into a bowl, then reheat the skillet.
Add the sausage and cook until browned, then drain the fat.
Stir the sausage into the cauliflower, then add the onion, oregano, salt and pepper.
Slice the tops off the peppers, remove the seeds and pith, then spoon the sausage mixture into them.
Place the peppers upright in a baking dish, then cover the dish with foil.
Bake for 30 minutes, then uncover and bake 15 minutes more. Serve hot.