Why wait?
It's not too late to put out swiss chard, kale, etc. if you can find plants at a garden center. I find these "renewable" greens really provide a great way to balance out the layer feed with something fresh and high fiber, along with spinach, which you can let bolt. The chickens went nuts for my huge cauliflower leaves also this spring, so I'm also doing a fall crop of about 30 plants of those. If they don't mature into heads for me, the leaves will still be great for chickens well into the fall. A row of only 6 cucumber plants climbing a trellis gave an endless supply of cukes for chickens and humans until just last week, and you can let fruit get big to have seeds for a little more nourishment. They enjoy all the usuals, like tomatoes, corn, peas, the later of which provide more protein. Clover is a great renewable crop with high protein.
I have grown sunflowers but not sure grains are really cost effective compared to the work it takes and the volume you would need to produce to truly replace a share of store bought food. Depends upon your ground, fertility, water situation, equipment, time etc. Oats are very easy to grow, but I think you would have to do it on a larger scale (e.g., with tractor) to have it pay off. Many other people are better informed than me about the grain crops and about other alternative grains, I'm sure. I had friends who grew lots of Amaranth, which seems highly productive. Every little bit can help.