Mix 1 tablespoon olive oil and garlic in a large microwave-safe bowl; heat on high until fragrant, about 45 seconds. Add chicken stock and heat on high until simmering, about 4 minutes. Gradually stir in couscous. Cover and let stand until liquid is absorbed, about 5 minutes. Fluff couscous with a fork.
Stir tomato, basil, vinegar, salt and black pepper into couscous; drizzle with remaining 1 tablespoon olive oil and sprinkle with feta cheese.