Place the bread in a large bowl. Coat with the olive oil and season with the salt. Line a cookie sheet with aluminum foil, spread the bread cubes on the cookie sheet, and bake until golden brown, about 20 minutes.
Place all of the ingredients in a blender (depending on the size of the jar, you may have to do it in several batches). Blend until smooth. Pour through a fine-meshed strainer to get rid of tomato and pepper skin and cucumber seeds. Chill for a couple of hours before serving. Serve the croutons on top of the gazpacho.