Cut courgette and bell pepper into quarters, then into coarse strips. Pour verjuice over it. Leave to rest for 20 minutes, stir from time to time.
Decant marinade into a container. Sauté finely chopped onion and garlic in a little olive oil until they become translucent. Add courgette and bell pepper pieces and let them fry. Add marinade little by little, repeatedly allow to boil down again.
Add oregano, close lid and cook slowly until done. Season to taste with pepper and salt. Sprinkle with Parmesam cheese before serving.