Any cover crops that I can still plant in Zone 4/Zone 5?

I am trying to rehab my backyard this year and had to have a large section of it excavated to fix some grading/drainage issue. However, that took out all the grass that was there before and the ground is currently fallow/bare. I am worried what will happen if I leave the ground as is through the winter - I am right in between Zone 4/Zone 5, so we'll typically have at least 3-4 months where there will be snow on the ground. With that being the case, I am wondering if there is anything I can plant there that will grow this year?

I also have some Kentucky Blue Grass seed that I could use but I think it's too late for seeding grass in my zone.

I do nt have experience with cover crops in zone 4/5 but as a general rule I observe what is dropping seed at the time of year that I am planting to know what grows with theat timing.  Mulching with grass hay ore weeds will supply seeds that may be naturalised to sprout in your zone now or when the snow melts.

winter wheat and barley are a little late but I'd still give them a try to fill the area.

as elle says, plus maybe theres winter rye that is an annual too, so it said on the label, I planted some last winter in some areas I tore top pulling logs and its still growing it took a couple weeks to sprout and I believe barley will grow too