It has been a while since we have seen the ears of wheat tiara I believe. Not even on Margriet. Or I may have forgotten it as it is always a disappointment when it is worn because much gets hidden in a hairdo.
The Queen wore two ears of wheat in her hair last week during the dinner for the international institutions but I imagine it will be the closest she will come to ever wearing it. And of course they may have been the other ears of wheat of the collection, not belonging to the tiara.
I don't think Beatrix ever wore the ears of wheat tiara either. Wilhelmina wore them but as loose elements on a fabric, before the tiara was created.