Bring the water to a boil. Stir in the couscous, cover, remove from the heat, and let stand 5 minutes. Spoon the couscous into a medium bowl and mix in 2 Tbsp. of the oil, and the cheese, tomatoes, basil, olives, garlic, salt, pepper, lemon zest and lemon juice.
Preheat your grill to medium-high. Brush the prawns with the remaining 1 Tbsp. of the oil. Season the prawns with salt and pepper. Grill the prawns 1 to 2 minutes per side, or until just cooked through. Divide the couscous among 4 plates. Set two prawn kebabs on each plate and serve.
Note: Couscous is sold in the ethnic foods aisle.