Beat egg yolks until thick and lemon colored. Add cheese, breadcrumbs, parsley, and salt and pepper; stir well. Beat egg whites (at room temperature) until stiff but not dry; fold into yolk mixture.
Melt butter in a large ovenproof skillet over medium heat. Pour in egg mixture; gently smooth surface. Cook 5 minutes or until bottom is lightly browned. Transfer omelet pan to oven; bake, uncovered, at 350° for 8 minutes or until a knife inserted in center comes out clean. Fold omelet in half; transfer to a warm serving plate.