1/3 cup freshly squeezed orange juice
3 tablespoons olive oil
5 teaspoons red wine vinegar
2 medium garlic cloves, thinly sliced
2 teaspoons kosher salt
1 1/2 teaspoons packed, finely grated orange zest
1/2 teaspoon red pepper flakes
3 medium bell peppers, ends trimmed, seeds and stems removed, and cut into 4 pieces
2 medium globe eggplants, sliced crosswise into 1/4-inch-thick pieces
4 ounces chèvre (goat cheese), crumbled
1 loaf ciabatta, sliced in half horizontally and lightly toasted
3 cups baby spinach