Heat a large skillet or Dutch oven over medium heat; cook and stir beef stew meat and Italian dressing until meat is evenly browned, about 5 minutes. Add 2 cups water, beef bouillon, diced tomatoes, beef broth, tomato sauce, garlic, bay leaf, salt, oregano, and pepper to skillet; bring to a boil. Reduce heat to medium-low, cover, and simmer until meat is tender, about 1 1/2 hours.
Place potatoes, carrots, bell pepper, and onion in stew; cover and simmer over medium-low heat until vegetables are tender, about 45 minutes.
Combine flour and cold water in a small bowl; mix until smooth. Stir flour mixture into stew, bring to a boil; cook and stir until stew is thickened, about 2 minutes. Discard bay leaf before serving.