Combine first 4 ingredients in a bowl; stir well with a whisk. Heat oil in a 9-inch cast-iron skillet over medium heat. Add breadcrumbs; cook for 1 minute or until lightly browned. Spread egg mixture evenly in pan; top with cheese. Broil 15 minutes or until omelet is firm. Sprinkle with onions, parsley, and oregano. Cut into wedges.