Saute Onion And Garlic In Oil For 5 Minutes. Add Tomatoes, Lemon Juice, Oregano, Salt And Pepper. Bring To A Simmer And Cook For 15 Minutes. Add Shrimp And Cook Until The Shrimp Turn Pink. Sprinkle With Feta And Remove From Heat. Toast Bread In Toaster Or In Broiler. Spoon Over Shrimp Sauce, Sprinkle With Olives And Parsley And Serve.