I've planted a fair amount of oats, and have been involved with harvest, in addition to planting them for food plots, I can share some of what I have seen.
One year field tillage was done, moldboard plowing, followed by a heavy disc harrow, in clay/loam/ with a little gravel mix type soil. The oats were broadcast and the last pass was a cultipacker. The germination of the seed was good, but there was a noticeable amount of ungerminated seed still on the surface. If wet weather persisted, those remaining seeds may have also germinated, even without a lot of cover, the root still penetrates the soil, and I have seen the same thing happen after harvest, whereas the oat grass came back and most if not all spilled oats on the surface germinated within the field. Field was sprayed for weeds as well. Crop was good, yield was good, and 10 700 lb bales of straw came off it. That year, all of the oat grass came back and even headed out again, you could have baled it, harvest would not get much grain but due to rains and weedkiller, I was amazed, turned into one big food plot for deer, was counting 30 in there often.
Following year, same tillage, oats drilled in, germinated fine, crop was fine, weed killer applied and I believe some additional fertilizer, I helped harvest and hauled the grain the to the buyer myself, the bale count was five more, 15 total, which fills the tandem grain/sileage body Mack DM we used to haul it. Quite a bit of oat grass came back but there was less rain and more weeds.
On my own , I have moldboard plowed, made 1 pass with a mounted disc, then broadcast oats, made another pass with the disc, mid to late august, and the results were excellent, I think a little earlier, and depending on rain, temperature overall weather, PH and fertility being right, oats seem to like nitrogen, you could make a decent grazing stand for the fall.
What you describe, broadcasting on untilled ground would seem to be marginal or less, really don't think without going to no till or some tillage to get some soil loose and make decent contact to the seed, the results will be dismal.
I learned a lot by helping my farmer friend an on my own, I also enjoyed the heck out of planting several food plots, and as much as a pest deer are or can be, we take a few annually for food, they were finished on oat grass which is high in protein, the meat was excellent, of course they browse for the most part but boy did they graze the heck out of what I planted, its like having a herd without fences, water trough's vet bills and what have you.
