There are a few vegetables that dogs shouldn't eat, and they are: onions, garlic, chives, leeks, shallots, scallions, and any vegetable in the allium family. These vegetables can cause anemia in dogs if eaten in large enough quantities. Other vegetables that are harmful to dogs include rhubarb leaves, tomato leaves and stems, potatoes (raw or unripe), and avocados (the fruit itself is safe for dogs to eat).