Hay
About 85% of what they eat should be hay. Fiber is necessary for a rabbit's digestion. Lack of this essential fiber can lead to dental disease and long-term GI issues. Rabbits should be eating their size in hay daily, not their weight, but a pile of hay roughly the size of their body.
Timothy hay is typically the best hay for a rabbit's diet. Bunnies seem to prefer 2nd or 3rd cut hay. These hays are softer and contain fewer seed heads than 1st cutting hay. At our shelter store(open only to members), we sell 5, 10, and 25-pound boxes of Timothy Hay from Small Pet Select and Grandpa's. Try one and see which your rabbit prefers.
A bunny food pyramid. Mostly hay and greens, a small amount of pellets and a berry treat.
"Oat hay is an excellent source of fiber for bunnies; it's great as a treat or during heavy sheds to aid their digestion."
However, if you are allergic to timothy hay, there are some alternatives. Orchard Grass, Meadow Grass, Brome, and Mountain Grass are potential substitute hays. We carry Orchard Grass at the Shelter. Try Farmer Dave's Clover Hay(not for everyday use) for a treat. Some rabbits also enjoy oat hay, which can be purchased occasionally at our shelter store or from Small Pet Select. Oat hay is full of delicious oat groats and very high in fiber, it's great for shedding season to help aid digestion.
Legumes like alfalfa and treats like clover should not be used as daily hay for rabbits. They are too high in fat and protein.