Brown hamburger and onion in fry pan. Add taco seasoning, and water. Simmer until thick (about 15 - 20 minutes). Stir occasionally so it doesn't stick.
Drain beans and stir into the meat mixture after it's thickened. Place lettuce in a large bowl and add beef and bean mixture. Add Fritos, chopped tomatoes and olives. Mix in enough Catalina Dressing to coat the ingredients. Top with grated cheddar cheese.