From my limited experience with harvesting grains, I would say that oats have got to be one of the easiest grains to mow with a scythe, but one of the hardest to mow neatly. It practically jumps out of the way of the scythe blade, but the grain heads fall to the right, or every which way, unless you use a grain cradle. "Where can I get a grain cradle?", you ask. If I could get them, believe me, I would carry them. Unfortunately, I don't know of anybody that still manufactures a grain-cradle. It's on my list of products to develop for 1SR, but until then you will have to make your own.
Or.... you could try this simple technique. In the video below, these people are implementing a brilliant idea that I have not seen, or heard of before. An assistant to the scyther, holds a light pole against the standing grain, for the scyther's next stroke, which keeps it from falling over, and apparently has the effect of guiding the stalks to move over to the left, just like it would with a grain cradle! I can't wait to try this myself! If any of you get to it before I do, let me know how it works out.
I found another video of this technique, where an assistant presses a pole against the standing grain, as it is being cut, in order tp prevent it from falling and scattering back towards the mower.