Which green vegetable is a common ingredient in dog food?

Green peas.

Green peas are a common ingredient in many types of dog food. Not only do dogs find them tasty, but green peas are also low in calories and high in many nutrients, making them a healthy treat for your dog

However, only feed your dog fresh or frozen peas, not canned ones. Canned peas are often loaded with salt, which is harmful to dogs in large amounts

Text source: https://www.healthline.com/nutrition/human-foods-for-dogs#section23