Spray 5- to 6-quart slow cooker with cooking spray. Cut beef into 1-inch cubes. In large bowl, toss beef with flour and 1/2 teaspoon of salt. In 12-inch skillet, heat oil over medium-high heat. Add half of the beef; cook and stir until browned. Remove from skillet to slow cooker. Repeat with remaining beef; discard flour. Add onions, carrots, celery, wine, tomatoes, broth, beans, 1 1/2 teaspoons salt, pepper and thyme to slow cooker.
Cover; cook on Low heat setting 8 hours. About 20 minutes before serving, in 4-quart saucepan, heat 4 cups water to simmering over medium-high heat. Stir in polenta; reduce heat. Simmer 2 minutes, stirring constantly, until polenta thickens. Stir in cheese and remaining 1/4 teaspoon salt. Serve stew over polenta.