Q. May I use Matzos made from Whole wheat for the Pesach Seder?
Q. May I use Matzos made from sources other than wheat, for example, spelt or oat?
Q. May one use "Gluten-Free" matzos?
Rosh Hayeshiva Shlit"a : In the shiurim at the yeshiva, we elaborated on the underlying issues involved. The details are long and complex. The answer to your question in short is :
There are two requirements in the "ingredients" of a Matzo 1] That it should be made from the "Five Grains," which are Wheat, Barley, Spelt, Oats, and Rye. When made from these five grains, it receives a status of "Lechem" [bread]. Matzos must first and foremost be a "Lechem Oyni."
2] It must be made from an ingredient that is "Royi Lh'achmitz," which means that it is "potentially" able to become Chomaitz—and because it is watched and baked in haste, never did actually become Chomaitz.
The question is, are these two requirements independent, or are they connected?
Is the requirement of "Able To Become Chomaitz" what makes these five grains the ingredients of Matzo — for only these five grains can become Chomaitz. Or is the requirement of "Able To Become Chomaitz" a separate requirement.
[ In other words, is "Royi Lha'cmitz" a Din in the Minor is it a separate Tna'i in the Matzah ]
If indeed "Royi Lhacmitz" is a separate requirement, it would follow that any of the five grains — including even wheat — if the Gluten were to be removed (as is done for the sale of wheat products for Celiacs and some restricted diets) which disables the dough from Leavening and becoming Chomaitz could be a problem.
In conclusion :
Whole Wheat Matzos: Wheat can become Chometz, but the chaff [bran] part cannot. A matzo which is "mostly" bran, may not be used. A matzo made of mostly bran would lack the first of the conditions that a matzo must be a "Lechem" a bread. Bran can not make "bread."
When using whole wheat matzos that are "mostly wheat," no added matzah for the shiur 'Kazayis" is needed to compensate for the bran part. This only holds if the whole wheat is from the entire wheat ground in its original form. If bran were to be separately added afterward, more matzah would need to be consumed to reach the shiur kazayis. This understandably would be hard to evaluate, and so a good suggestion would be to acquire whole wheat Matzos under a competent Hashgacha that would be knowledgeable of the above requirements in producing whole wheat matzos.
It must be mentioned that there are many [for various reasons] who prefer only using well-ground pure flour matzos, removing all the bran and chaff. On Pesach, each should follow the custom and stringencies of his family and community.
Oat matzah and spelt Matzah: There is a discussion in the poskim if the "Quaker oat" is, in fact, the "Shiboles Shual" — the fourth grain listed in the list; of the "five grains." There is also reservation in using any other grain other than wheat for two reasons 1] what is the preferable grain used to make bread, and so the matzah bread should L'chatchila be of wheat. 2] we know, as passed down from generation to generation, the "allotted Time" for matzah to be baked so that it should not become chometz we do not have the same clear guidelines baking a Matzah with the other grains. It is the opinion of Maran Rav Eliyashiv Zt"l that oat and spelt matzos may indeed be used.
If possible spelt "may" take precedence over Oat for the Matzos Mitzvah, it is mentioned in the "list of the five grains" before Oat, and possibly it is more of an honorable form of bread.
Gluten-Free Matzos: One should "preferably" avoid using "Gluten-free" Matzos for the Mitzvahs Matzah. If need be, Oat Matzos, which are "naturally" gluten-free, should be used. This follows the opinion of Maran Rav Elyashiv zt"l