Paytonjpk; what count to determine the food is not the age of the rabbit (some people give unlimited pellets under 6 months, but that's it). It's the size. You can't give the same amount to a Continental Giant and a Nethie the same way you wouldn't feed a Chihuahua and a Newfoundland the same amount of dry food... The house rabbit society indeed gives good guidelines. You have to calculate the vegetables and pellets amount in % of the rabbit's weight. In the end, the whole thing should be around 10% of the rabbit's weight (about 8% in vegetables, with 2/3 of leafy greens 1/3 of other things, and 2% in pellets) a day, plus the rabbit's body (visually, not the weight this time) in hay.
Pellets aren't a necessity, like Blue eyes said, some people go with a pellet free diet. It's sometimes recommended for rabbits who have reoccuring GI stasis problem. They should never be a big part of the alimentation in any case.
That said, I myself decided to keep giving pellets (very little, my rabbits get about 20g for the both of them) because I thought it was very complicated to get a balanced diet with all the necessary nutriments with only vegetables. It's of course possible, and it's probably easier with a bit of practice, but it means really looking at everything to plan good menus. It's also a bit difficult to maintain during some months of the year when you go with locally produced vegetables (which I try to do - March is a terrible month, winter vegetables are out and spring vegetables are not available yet).
On the other hand, you have to be very careful not giving too much of them and to chose good pellets (lots of them have molasses, grains and nasty stuff in them). Rabbits get chubby really easily and too much pellets often means the rabbit doesn't eat as much hay has he could which could lead to a problem during a moulting period or when the rabbit will be scared / older and that the guts won't work as well as they should).