Season chicken with salt and pepper. Cook in 2 teaspoons oil over medium-high heat, 4 to 5 minutes on each side, or until done. Remove from pan and keep warm.
Add remaining 1 teaspoon oil to pan; add oregano, basil, garlic and tomatoes. Cook over medium-high heat 3 to 5 minutes, or until tomatoes soften.
Meanwhile, cook couscous according to package directions.
Place ½ cup cooked couscous on each of 6 plates. Slice chicken and divide evenly among plates. Top evenly with tomato mixture, cucumber, and feta cheese.