I have recently made oatmeal, I put a few cups of quick oatmeal in blender, put some hot water and then pulse in blender until thickened. I then dropped 3-4 whole (in shell) boiled eggs into the mix. It made this gruel looking slop, but they went crazy for it. Oatmeal is relatively cheap. I gave it to them warm, not hot on a cool rainy damp day. They were cleaning each others beaks off where it slopped.
They also like tomatoes from the garden, any fruit (grapes are a fave), yogurt and cottage cheese. Also my boys eat lots of apples, so I save the cores for the day and throw them in and they love those too.
I usually end up giving snacks to them when still in date and good, but close to when I would toss them. Good way to clean out refrigerator if anything got shoved to the back and I already bought a new one, etc.