Brown ground beef in 2 tablespoon hot oil in frying pan. When almost browned, add onion and continue browning until onion is tender. Pour meat and onion into 3.5 quart crockpot. Add puree, sauce, paste, water, salt, pepper and oregano and set dial on low setting. Cut 2 lbs. sausage into pieces and brown in remaining 2 tablespoons oil. When brown, place sausages in sauce in crockpot. Continue cooking for dozen hours. (If you like your sauce sweeter, you could add quarter to half cup sugar to this.)