Heat oil in a frypan over medium heat. Saute onion in oil until transparent. Stir in spring onions and garlic; cook, stirring frequently, for 2 more minutes. Stir in tomatoes, wine, most of the parsley, oregano and salt and pepper to taste. Cover and simmer gently for 30 minutes.
Preheat oven to 260 degrees C.
Spread half the sauce on the bottom of a large oven dish. Arrange prawns evenly over sauce, and pour the remaining sauce on top. Sprinkle with feta cheese.
Cook in preheated oven for 10 to 15 minutes, until prawns are pink and the feta is melted and lightly browned. Sprinkle with remaining parsley, and serve immediately.