1. Heat scant 3 tbsp of oil in heavy skillet, add garlic and mushrooms and cook briefly. Add remaining oil, grapefruit juice, catsup, sugar, salt, mustard, tabasco and heat to just below boiling.
2. Place all the remining ingredients in a large glass bowl.
3. Pour hot marinade over the vegetables. Cover and marinate in the refrigerator for 12 hours or more. Stir occasionally.
4. Drain and serve.