In a large skillet cook ground meat and onion until meat is brown and onion is tender. Drain off fat. Stir in tomato sauce, bulgur, oregano, salt, and pepper. Bring to boiling; reduce heat. Simmer, uncovered, about 5 minutes or until desired consistency, stirring occasionally.
To assemble, arrange romaine on bottom halves of rolls. Spoon meat mixture on romaine. Sprinkle with feta cheese; replace top halves of rolls. Makes 6 sandwiches.