Roughly chop the tomatoes, cucumber, bell pepper, and red onion. Combine all chopped vegetables with the minced garlic, olive oil, vinegar, and the optional stale bread in a large bowl. Season with salt and pepper.

Using an immersion blender or a regular blender, blend the mixture until smooth. For a smoother gazpacho, pass the mixture through a fine-mesh sieve to remove any skins or seeds.

Cover the gazpacho and refrigerate for at least 2 hours, or preferably overnight, to allow the flavors to meld. Serve chilled, garnished with a drizzle of olive oil and croutons if desired.