Prepare couscous according to package direction. Leave covered and set aside.
Using medium-high heat, add the oil to a large skilllet and heat until very hot. Season the steak generously with salt and pepper and put it in the center of the pan. Add the beans, shaking the pan so they settle in the spaces around the meat.
Don’t move the steak around as it cooks, but shake the pan occasionally to brown the beans on all sides.
Add 2 Tbsp. of the dressing and cook 5 min. or until meat is browned on both sides, turning after 3 min.
Stir in garlic, tomatoes, mushrooms, and remaining 6 Tbsp. dressing. Bring to boil.
Lower the heat to medium and simmer about 10 min. or until meat is cooked to desired doneness and vegetables are crisp-tender.
Remove the steak from the skillet to a covered plate or cutting board, to rest. Leave the vegetables in the skillet.
Increase the heat to high, add about 1/4 cup water, and cook 1 to 2 minutes. Scrape the pan to dissolve any of the browned bits. Season with salt and pepper and remove from the heat.
Uncover the couscous, fluff it by scraping it with a fork, and then fold in the beans and tomatoes.
Taste for seasoning.
Slice the steak across the grain. Serve couscous on each plate; arrange steak slices over the couscous.
Pour any accumulated meat juices over the couscous.
Sprinkle with Parmesan, if desired.
Garnish with halved olives, and lemon or lime wedges to squeeze over all, if desired.