Cook couscous in water as directed on box, omitting oil; cover to keep warm.
Meanwhile, in 8-inch square (2-quart) microwavable dish, arrange bell pepper halves; add 2 tablespoons water. Cover with microwavable waxed paper. Microwave on High 3 to 4 minutes or just until crisp-tender.
Stir spinach and cheese into couscous. Spoon mixture into pepper halves.