The Ararat Scrolls

OK, so I am back after all, and Pesach has not even started...

Are oats to be considered chametz, grains not to be consumed if leavened (e.g. by fermentation) on Pesach?

I started with Wikipedia, even though I always take what I read there with a grain of salt.

The Torah (Exodus 13:3) prohibits Jews from eating leaven (chametz) during Passover. Technically, chametz is only leaven made from the "five grains": wheat, spelt, barley, shibbolet shu'al (two-rowed barley, according to Maimonides; oats according to Rashi) or rye...

Evidently we have some disagreement, going back a few years, about whether oats are prohibited. Searching some more (and thanking God for Google), I landed on a JTS document, Haggadah Shel Pesah (in PDF, and very interesting for more than this short quotation):

The five grains which can be used to make halah, and therefore can become
hamaiz and are prohibited on Passover are:

Hitim - wheat [Triticum durum and vulgare]
Se'orim - 6- and 4-rowed barley, [Hordeolum sativum and vulgare]
Kusmim - {Even Shoshan=Triticum dicoccum, J Cohen=spelt}emmer/lesser spelt/ rice wheat
[Triticum dicoccum]
Shibbolet Shu'al - {Even Shoshan=Avena; J Cohen=oats}2-rowed barley [Hordeolum distichum]
Shippon - {Even Shoshan=Secale=rye, JCohen=rye} spelt wheat [Triticum spelta].

These are the only items which can become hamaiz. While there is virtually total rabbinic agreement since Talmudic times that these Biblical Hebrew terms comprise the sum total of items which can become hamaiz, there is not agreement regarding the proper translation of the terms kusmim and shibbolet. Some authorities include oats in the above list but it is doubtful whether oats should be included. [my emphasis]

(This source also suggests that the inclusion of rye on the prohibited list, according to most authorities, is inaccurate.)

Kashrut.org agrees that oats do not belong on the list:

The Gemara says in Menachot 70a, and so it is brought down in the Halachah, that the five grains are either types of wheat or types of barley (two are wheat & three are barley). Oats does not fit in to this category. It is not a wheat nor is it a barley. Clearly some people went to great lengths to randomly translate each of the five grains into something in English without regard to the consequences. People are being restricted unnecessarily, and others are making a Bracha LeVatalah on Matzot made from Oats. One who uses oats for Matzah is absolutely not Yotzeh (accomplishing) the Mitzvah.

My oat granola will remain on the breakfast menu this Pesach.