Place a rack in the middle of your oven and preheat to 300°F. Slice day-old (or fresh) bread into 2 x 2-inch cubes and place in the sheet pan. Drizzle wit olive oil and toss to combine. Bake until toasted, about 20 minutes. Fresh bread will take about 5-10 minutes longer.
While the bread toasts, wash all of the produce. Slice cherry tomatoes in half. Cut the cucumber in 1/2 inch thick quarter rounds. Slice the nectarine into 1/2 inch thick slices. Slice red onion in 1/4 inch thick half moons.
Once the bread has toasted, pull it from the oven, and allow it to cool.
Add the toasted bread to a very large bowl and top with salad greens. Top the greens with tomatoes, nectarines, cucumbers, and red onions. Finish with mozzarella pearls (not pictured here.)
Add the remaining olive oil, the vinegar, and the salt to a small mason jar or another container with a tight-fitting lid. Close the lid tightly and shake the oil and vinegar until combined. Dress the salad. Toss to coat.
Let the salad sit for at least an hour to allow the bread to soak up the dressing. Serve and enjoy!