• Step 1: In a large bowl, combine the drained and rinsed kidney beans, garbanzo beans, and green beans.
• Step 2: Add the diced red onion and celery to the bowl with the beans.
• Step 3: In a small bowl, whisk together the apple cider vinegar, olive oil, sugar, oregano, salt, and black pepper to make the dressing.
• Step 4: Pour the dressing over the bean mixture and stir gently to coat everything evenly.
• Step 5: Cover the bowl and refrigerate the three bean salad for at least 30 minutes, or up to 5 days, to allow the flavors to meld.