Heat oil in a large nonstick skillet over medium-high heat; add onion and garlic. Cook 4 minutes, stirring occasionally, until golden. Add peppers and squash; cook 5 minutes, stirring occasionally, until vegetables are tender.
Cook couscous according to package directions, using chicken broth instead of water and omitting salt and fat. Stir in vegetable mixture, pine nuts, basil, and black pepper.