In a skillet, cook beef and onion over medium heat until meat is no longer pink.
Add garlic; cook 1 minute longer. Drain.
Stir in tomato sauce, water, tomato paste, salt and oregano.
Spread one-fourth of the meat sauce in an ungreased 5 qt. slow cooker.
Arrange one-third of the noodles over sauce (break noodles if necessary to fit).
Combine cheese; spoon one-third of the mixture over noodles.
Repeat layers twice. Top with remaining meat sauce.
Cover and cook on low 4-5 hours or until noodles are tender. Yield: 6-8 servings.