Guinea pigs eat most dark leafy lettuces, including romaine, green leaf, red leaf and butterhead lettuce. They also eat non-lettuce greens, such as mustard, spinach, chard, arugula, kale, beet tops, radicchio, cilantro and parsley.
Other vegetables eaten by guinea pigs include bell peppers, carrots, tomatoes, broccoli, corn silk, dandelions and celery. While most greens are safe, guinea pigs should not eat iceberg lettuce, which has high water content and a low nutritional content. Guinea pigs should have fruit only in small amounts due to its sugar content. Guinea pigs should eat around 1 cup of vegetables daily, with the majority being leafy greens or lettuce.