Preheat oven to 350 degrees. In a large skillet, melt butter over medium-high heat. Add the garlic, shrimp, oregano, and pepper flakes. Cook until the shrimp are just pink, turning once (about 3 minutes). Transfer the shrimp to a large shallow casserole (or individual gratin dishes). Arrange shrimp in a single layer. Add the vermouth to the skillet and boil until liquid is reduced by half. Add the chopped tomatoes and stir until heated through. Top the shrimp with the tomato mixture and crumbled feta. Bake until the cheese is bubbly, 8-10 minutes. Sprinkle with minced parsley and serve. 6 servings.