Prepare grill (medium-high heat). Brush sliced Vidalia onions with olive oil, season with salt and pepper. Grill onion slices and peach until tender, about 4 minutes per side. Thinly slice peaches.
For the dressing, simply whisk together all ingredients in a bowl. In another large bowl, toss together the salad, freshly grilled sliced peaches and Vidalia onions. Drizzle with dressing and sprinkle goat cheese on top. Serve immediately.