Meanwhile, cook and stir steak in 2 Tbsp. of the dressing in large skillet on medium-high heat 2 min. or until steak is browned on all sides. Stir in tomatoes with their liquid, the onions, peppers, mushrooms and remaining 2 Tbsp. dressing. Bring to boil. Reduce heat to medium; simmer 10 min. or until onions and peppers are crisp-tender. Remove from heat.