The Gemara in Pesahim (p. 35) and Menahot (p. 70) discusses the five grains. In Hebrew, they are Hita, Se'orah, Kusemet, Shifon and Shibolet Shual. Hita is wheat. Se'orah is barley. The traditional translation of Kusemet is spelt, and Shifon is rye. Shibolet Shual is classically identified as oats. This is based on Rashi who offers the vernacular "Avina" as translation. Avina in French is oats. This is also the first interpretation of the Aruch, as well as other Rishonim of Ashkenaz, including the Bartenura's commentary on the Mishna.
Only these five grains are susceptible to becoming Hames. Accordingly, only these grains can be used to make Masa. Only a grain that can potentially become Hames may be used for Masa. There are other Halachic ramifications of being classified a grain. Only dough made from these grains is obligated in separating Hallah. Also, only these five grains can constitute bread to recite the Beracha of Hamosi and Birkat Hamazon.
In recent years, there was controversy surrounding the identification of Shibolet Shual as oats. Rabbi Dr. Yehuda Felix published a book through Bar Ilan University about the botany of Eres Yisrael in the times of the Mishna. Based on his research, he brought proofs that Shibolet Shual cannot mean oats. First, he claims oats did not exist in Eres Yisrael in the times of the Mishna. Moreover, oats have different characteristics than the other four grains. For example, oats do not contain gluten, whereas the other four grains do
If he is correct, oats cannot be used to make Massot. They also would never become Hames, and they would not be obligated in Hallah or Birkat Hamazon. Nevertheless, the modern Poskim, including Rav Moshe Feinstein, Rav Elyashiv and Rav Shlomo Zalman Auerbach, concur that we must be strict and treat oats as potential Hames. Rashi's identification cannot be overturned based on academic findings. The Rambam has already established that tradition and custom are the basis of Halacha. A recent populist article claiming that Rashi was wrong and that oats are not Hames is not only without any scholarly support, but it is presumptuous and reflects the authors bias against the rabbinic establishment. (listen to Audio for detailed critique of this position).
Not only do the Poskim stand by the identification of Shibolet Shual as oats to treat it as Hames, but they also permit someone with Celiac to fulfill the Misva of Masa with oat Masa. Of course, it is better to bypass the controversy altogether and eat spelt Masa, if possible.
SUMMARY
Oats are a grain that can become Hames. If a person can only eat oats, he may fulfil the Misva using oat Masa and recite the Beracha of Hamosi.
