Heat oven to 375°F.
In large nonstick sauté pan, heat oil over medium-high heat. Add garlic, spinach and Italian seasoning and cook, stirring constantly, until spinach wilts, about 3 minutes. Drain off excess liquid. Stir in half of the chopped pepper. Remove from heat.
Place chicken in small baking dish. Place spinach mixture on top of chicken breasts, dividing evenly. Cover with foil and bake at 375°F for 20 minutes. Remove foil; top each with sliced cheese. Bake, uncovered, 5 more minutes.
Meanwhile, bring chicken broth to a boil. Remove from heat; stir in couscous. Cover and let stand 5 minutes. Stir in remaining chopped red pepper. Serve chicken with couscous on the side.