Heat gas or charcoal grill. Remove tofu from marinade, reserving marinade; set aside. Cut 18x18-inch sheet of heavy-duty foil; fold or roll up edges of foil. Spray foil with cooking spray. Place bell pepper and onion on foil; drizzle with reserved 2 tablespoons marinade. Place on grill over medium-high heat. Cover grill; cook 5 to 6 minutes, turning occasionally, until tender. Place tofu on grill next to vegetables. Cook 4 to 6 minutes, turning once and basting occasionally with reserved tofu marinade, until lightly browned. Remove vegetables and tofu from grill to plate; cover to keep warm.