adebourget wrote: I wonder if these mushroom are edible?

I'm not sure how to post a photo to this forum so you can see - if you have instructions for that let me know and I'll post. Thanks!
I can not say if the volunteer mushrooms in your garden are safe to eat.
I will say they will not hurt or make your vegetables un-safe to eat.
Annual vegetables have a different relationship with mushroom families than woody plants do. But all living plants have some mutual relationships with mushrooms in general. They too are part of the microherd you've been hard at work supporting in an organic garden.
Most of a mushroom you will probably never notice in the soil. A toadstool is just the fruiting body of this specie.
If it looks objectionable, simply weed it out.
As to how did they get in your garden? At some time in the past either a tree grew there, or bark mulch (or lumber waste) was buried there, mycellium which has a close working relationship with trees are simply sending off the children (spoor) to their new homes.