A few questions in regards to making ‘bread’ from oats…
If someone takes whole oats (doesn’t first make it into kemach) and mixes it with water, oil, etc making some sort of mixture from it and then bakes it in the oven. Does this have the din of lechem? What bracha should be made on it? What if they kavuah a seudah on it? And also in regards to using it for lechem mishneh in seudas shabbos.
And one more point, does challah have to be taken from such a mixture?
In priciple, oats receive the mezonos berachah only when cooked, as in oatmeal, porrige, and so on. In this case hamotzi is not relevant, because the food is not baked.
It is also possible to create “oat flour,” which is how oat matzos are created, after mixing with water. There is difficulty in this due to the absence of gluten, and techniques have been invented to achieve the desired results.
However, where the oatflakes do not stick together in a porrige form, or as a dough, they retain the ha’adamah blessing, even if they are roasted/baked (according to most poskim, granola bars are ha’adamah, even though the flakes are stuck together with honey etc.).
Therefore, from the sound of it, the mixture you refer to will not have the status of mezonos of hamotzi, and its blessing will remain ha’adamah. As a result, it cannot be used for Shabbos, and no challah is taken.
The poskim discuss the status of oatflakes concerning granola bars and similar foods; see Vezos Haberachah p. 106. The general principles of a food belonging to the five grains becoming mezonos are found in Siman 208; see Beis Yosef; Mishnah Berurah 7;Be’er Heitev 6.