Any seasonal vegetables can be used in this sandwich so feel free to substitute your favorite veggies.
With a pastry brush, brush olive oil on the vegetable slices and the mushrooms caps. Season them with salt.
Place vegetables on a hot grill and cook until they are tender. To assemble, slice mushrooms into 1/4-inch slices, spread both sides of the bread with goat cheese and then top with 1 slice each of grilled vegetables and a quarter of the mushrooms.
Top with spinach and remaining piece of bread. Serve.