According to About.com, pet rabbits should have a diet that is mainly composed of fresh grass hay and vegetables. Pellets and occasional treats may be added as well to provide some variety.
Fiber plays an important role in regulating a rabbit's digestive system, and the fiber found in grass hays and vegetables ensures that the rabbit is not at risk for obesity or other digestive problems. While pellets are rich in nutrients, experts have found that rabbits overfed on pellets are at risk for many health-related problems. Therefore, it is advised to restrict pellets in a pet rabbit's diet and to compensate with grass hays and vegetables. As for treats, the House Rabbit Society recommends 1 to 2 tablespoons of fresh fruit per day.