Frost tolerant seedlings

Hi I was curious if anyone knows of anything you could direct sow in the winter with success? Hardy to 15°F or more.

I read this article https://www.thefreelibrary.com/Frost+tolerance+of+ten+seedling+legume+species+at+four+growth+stages.-a081111134
Which was useful but most of the edible plants besides soybean (navy beans and pinto beans) only could live at 25° fahrenheit.

I would like to not have to do the greenhouse method of direct sowing. I prefer to not have to cover and uncover plants daily. If I leave them covered the sunlight during the day scorches them. Thanks

Almost no plants will benefit from below freezing temps outside established perennials. But some will germinate just above freezing. Typically though they MUST stay above freezing until they can establish a bit, or the water in the plant crystalizes and busts open the plant cells and they die.

https://harvesttotable.com/vegetable-seed-germination-temperatures/

There are some sparse useful trees and flowers that are edible that require cold-stratification, like lavender, but I'm not sure that's what you're looking for really.

The site you linked talks about legumes.
The most frost tolerant are faba beans which here in Germany are sown around February, they tolerate frost well.
Peas not so much.

But apart from these, there are many more vegetables that can be "winter sown": You prepare the seed trays and put them outside with a cover in an area that is protected against storms and too much sun. Then when the seedlings get the right temperature impulse, they start to grow. When temperatures drop again they just go into a kind of standby status but don't die.

These include:
salads (lettuce)
parsley
onions, leeks
dill
as well as flowers

In the US, many people use milk jugs. When you google winter sowing you get lots of sites.

The main advantage is that you don't need lots of spaces indoors but really only have to wait and monitor a bit.

If you don't have much slug pressure you can also start your winter sowing at the end of autumn (carrots, peas).

To add on to Anita's excellent post, there's a whole site about this:  http://wintersown.org/

Which used to have a vibrant community at GardenWeb (um, 20 years ago or so).  It looks like they've just refreshed the website, which is awesome.  It's not direct sowing, but it will get you seedlings early with little work.