Place a grill pan over medium-high heat or preheat a gas or charcoal grill.
In a small bowl, mix together the olive oil, garlic, sun-dried tomatoes, basil, tarragon, thyme, salt and pepper. Place 2 tablespoons of the mixture in a medium bowl. Add the zucchini and eggplant to the medium bowl and toss until coated. Place the vegetables on the grill and cook for 3 to 4 minutes on each side until tender.
While the vegetables are cooking, spread the olive oil mixture on the baguette halves. Using a spatula, spread the goat cheese over the olive oil mixture. Place the cooked vegetables on the bottom half of the baguette. Arrange the spinach on top of the vegetables. Place the top half of the baguette on top of the filling.
To serve, cut the baguette into 4 sandwiches. Serve immediately or wrap in parchment paper and refrigerate for up to 2 hours.