Put the bread cubes in a large bowl and add the tomatoes, cucumbers, parsley, peppers, cucumbers, and onion. Add the feta and olives and feta and toss to combine.
Whisk together the lemon juice and Dijon mustard in a medium bowl. Whisk in the olive oil.
Pour the dressing over the ingredients in the large bowl and toss to combine. Season with salt and pepper and toss again.