Bring a large sauce pan of water to boil, add the macaroni and peas. Cook until pasta is al-dente, according to package instructions. Strain through a colander into a medium bowl, and set aside.
Mix together the cooked pasta and peas with the cream of mushroom soup, celery, onions, and tuna.
Rub a casserole dish with olive oil. Pour the mixture into the dish, then top with cheddar cheese and bread crumbs. Cover with foil, and bake for 30 minutes.
Remove foil, garnish with parsley, and serve warm.