1. Place lentils in a colander, rinse in cold water and drain.
2. In a medium saucepan, bring water to a boil. Add lentils, reduce heat to low, cover and cook for 15 minutes.
3. Add onion and carrots. Cook 15 minutes more or until lentils are tender.
4. Remove from heat and cool slightly.
5. Stir in bread crumbs, egg, garlic powder, oregano and salt.
6. Melt margarine in large skillet. Drop lentil mixture by rounded 1/2 cupfuls into hot margarine. Flatten mounds into patties and cook until firm and golden brown on both sides.
7. Top each patty with a thin slice of cheese.
8. Serve immediately.
9. Refrigerate leftovers within two hours.