Preheat a grill to medium-high. Brush the bread, ham and peaches with the olive oil and season with salt and pepper. Arrange on the grill and cook, turning once, until the bread is slightly charred and the peaches are softened, about 5 minutes, and the ham is slightly charred, about 8 minutes. Let cool.
Thinly slice the ham, cut the peaches into thick wedges and cut the bread into large cubes. Using a food processor, puree the avocado with the buttermilk and lemon juice; season with salt and pepper.
In a large salad bowl, combine the spinach, ham and peaches. Add the avocado dressing, season with salt and pepper and toss. Top with the croutons and goat cheese.