They love all sorts of greens, ie grass, clover weeds. Turkeys are the only animals that I have that will eat lemon balm, which is good because I was on the way to having nothing but lemon balm in some areas, since it reproduces like a weed, but they are eating it faster than it can grow.
Once mine are past the baby stage, I put mine out on pasture. They spend a large part of their day grazing for greens, bugs, and worms. Plus they get to hunt for those little bonuses that the cows leave in the fields.
I supplement my cattle feed with free local onions, and the turkeys love them. (not turkey related, but the ducks will take onions pieces, wash them in the mud, and then eat them.)
I supplement with local wheat, home grown corn (sweet corn in the summer, Indian corn in the winter), and lots of fruits and vegetables. (Waste farm produce) Mine also love sunflower seeds as a treat, but they can be on the expensive side. So watch out for sales. Frankly at $18 a bag for turkey feed, as it is in my area, it makes no sense to feed them only commercial feed for very long. I figure that my birds get 75% of their feed from grazing and 25% from feeds that I providel
Mine are happy, look healthy and have beautiful feathers, so I must be doing something right by avoiding all those $18 a bag of commercial feed.. The commercial feed people would like you to believe that all livestock would die without them. But the US has a very large wild turkey population. How do they survive without commercial feed? Of course, I live on a farm and my turkeys have acres and acres to roam, so you may not be able to feed your turkeys the same. And I live in the Pacific Northwest, where green grass is available year round. And I grow heritage birds, which are supposed to have a little more brains. But you wouldn't know it if you hung around them for long.