I used the meat bird formula made by Nutrena for my last group- I think it was 22% protein. I have no idea how much they ate, but they dressed out at 5-6 lbs at 7 weeks and were fabulously delicious :).
I have 25 more chicks arriving at the end of August. I just started raising mealworms today, unfortunately my guys don't get a lot of grass access but I used to give them 1/4 cup of dried meal worms and 1/4 cup of scratch grains every morning and they LOVED it. No, I'm not really that retentive that I actually felt the need to measure their bugs and scratch, it just happened to be the available scoop :)
I really want to provide my birds with more good quality forage. I am going to try to sprout some alfalfa indoors and offer it to them daily and see what they think about it. I got this crazy idea from the FarmTek catalog where they were showing hydroponic systems to grow up to 2,000 lbs of forage a DAY for livestock. I think I can do something smaller scale in my kitchen since I sprout all the time for the humans to eat.
I don't have access to organic feed reasonably close to me, but I was happy with the Nutrena products overall. I am hoping that my mealworm farm/microsized hydroponic sprouting operation will help reduce my feed costs. It may end up being a huge bust, but I will be sure to post some photos!