Cut 4 large tomatoes in half horizontally. Scoop out pulp from each tomato half, leaving shells intact; discard seeds and coarsely chop pulp. Stir together pulp; 4 ounces crumbled feta cheese; 1/4 cup fine, dry breadcrumbs; 2 tablespoons chopped green onions; 2 tablespoons chopped fresh parsley; and 2 tablespoons olive oil in a medium bowl. Spoon mixture evenly into tomato shells, and place in a 13- x 9-inch baking dish. Bake at 350° for 15 minutes. Garnish with Italian parsley sprigs, if desired.