CUT steak into 6 equal portions; place in large baking dish sprayed with cooking spray. Mix steak sauce, dressing, onion and garlic; pour over steak. Cover. Marinate 1 hour in refrigerator.ADD potatoes and mushrooms to ingredients in baking dish; cover.
BAKE at 350°F for 1 hour or until steak is cooked through and potatoes are tender, adding frozen vegetable blend to baking dish after 45 minutes.
* It says to marinate the meat for one hour...I did more than an hour and it came out VERY tender.