First of all, our previous bunny and our now two baby flemmish babies eat an almost an entirely diet of green leafy vegetables. Munching pellets if they want. You can read Google articles about what to feed rabbits. It gets to be involved...for instance Kale is OK except in large amounts it puts too much calcium crystals in their bladder..etc. I think also for brussel sprouts....broccali..etc, I don't think it's good for them in large quantities..certainly no problem with a little bit here and there to vary their diet. ....Remember in their far long ago wild state, they were grass eaters and opportunistic leaf munchers.
Our rabbits have all the oat hay they want to eat, and their next vegetable is carrot tops (obtained from farmer's market), romaine lettuce, fennel leaves, cilantro , parsely, and of course, oat hay and course oat kernels. And pellets whenever they want.