Prep charcoal grill with medium-hot coals or heat gas grill to medium-high.
Using 12-inch-wide heavy-duty aluminum foil, cut 4 pieces 32 inches long; fold each piece in half to make a 16 x 12-inch rectangle. Generously coat foil pieces with nonstick cooking spray.
In a large bowl, stir together 2 teaspoons of the oil, 1/4 teaspoon of the salt and 1/4 teaspoon of the pepper. Toss with tomatoes and olives. Evenly place mixture on one half of each foil piece.
In the same bowl, combine garlic, lemon zest, remaining 2 teaspoons olive oil, 1/4 teaspoon salt and 1/4 teaspoon pepper, and mix well. Add shrimp; toss to coat completely. Divide shrimp evenly among packets, arranging over tomato mixture.
Fold second half of foil over shrimp and vegetables. Tightly seal sides and front edges, leaving space for steam to build. Place packets on grill rack; grill 12 to 15 minutes. Carefully open packets; transfer contents to 4 serving plates. Sprinkle each serving with chopped parsley, and serve with brown rice on the side. (See photo, page 172.)