In a plastic bag, combine 1/2 cup flour with the salt and pepper; toss with beef cubes to coat thoroughly. Place beef cubes in crock pot.
Place chopped green pepper and sliced mushrooms on top of beef cubes.
In a large pyrex measuring cup, combine beef broth, Worcestershire sauce, and tomato paste or ketchup. Pour over beef and vegetables; stir well.
Cover and cook on LOW setting for 7 to 12 hours. ONE hour before serving, turn to HIGH setting. Make a smooth paste of red wine and 3 Tablespoons flour; stir into crock pot, blending well. Cover and cook until thickened.