Legumes are really good for birds, but sometimes a pain in the butt to provide. The easiest way to feed lentils, beans and grains is to buy a packet of Soup Mix from the supermarket. These usually have lots of different types of beans and lentils in them, and some barley and split peas, etc. You just need to rinse it and boil it until it's tender, then feed it once it's cool. If it's got the barley in it then that looks like the little hulled oats in most seed mixes and should entice your tiel to try it.