Combine flaked albacore tuna, garbanzo beans, black olives, English cucumber, red bell pepper, green onions, and parsley in a bowl.
Blend balsamic vinegar, extra-virgin olive oil, garlic, dried oregano, and ground black pepper in a separate bowl using an immersion blender until garlic is pureed. Stir dressing into tuna and combine well. Serve over baby spinach.
