Boil vegetables in salted water for about 10 minutes; drain and reserve 1 cup of the vegetable water.
Cut steak into 6 serving-size pieces. Season with salt and pepper then dredge in flour. Pound meat to thin and flatten with meat mallet as for Swiss steak. On each serving of beef, place a slice of onion, a slice of green pepper, and mushrooms. Shape meat into rolls and fasten with toothpicks. Place meat in skillet with bacon drippings or oil and brown on all sides. Remove beef to a large casserole; place partially cooked vegetables around beef rolls. Add 1 cup of vegetable water or broth. Cover and bake at 350° for 45 to 60 minutes. Remove to a heated serving platter and serve with pan juices.