Preheat barbecue to medium-high. In a bowl, toss together peppers, zucchini, eggplant, 2 tbsp (30 mL) olive oil and the salt and pepper until well coated. Grill vegetables until just softened, about 5 min. per side. Transfer to a plate to cool.
In a small bowl, whisk together remaining olive oil and the red wine vinegar to make dressing. Set aside. Halve bread lengthwise. Layer grilled veggies on bottom half of loaf and drizzle with half the dressing. Sprinkle with goat cheese and spread spinach overtop. Drizzle with remaining dressing. Replace top half of loaf. Wrap sandwich tightly in plastic wrap. Refrigerate at least one hour before slicing to serve.
Slice this sandwich just before serving for easy transport and to give the flavours more time to meld together.