Cut 18-inch square of heavy foil; place vegetables in center.
Combine oil, garlic, 1/4 teaspoon salt, and 1/4 teaspoon pepper; drizzle atop.
Bring up opposite edges of foil and, leaving a little space for expansion of steam, tightly seal top, then each end.
Place in center of the cooking grill.
Grill 35 minutes or till vegetables are tender.