We have one area in our front lawn where a partial fairy ring periodically appears. The mushrooms of this ring are large and generally white, almost "picture perfect" mushrooms, in fact.
It turns out that they are the poster child for why you don't eat the mushrooms you find. If my identification is correct (and I think it is), these are false parasols, aka green spored parasols, aka Chlorophyllum molybdites. Many of the ones in our yard right now are 8" in diameter and they look delicious, as mushrooms go, but the information I could find said that they caused severe abdominal cramps, bloody diarrhea, and projectile vomiting about 1-2 hours after eating. They are apparently the mushroom most often causing accidental poisonings. I only found one reported fatality, but they sure don't sound like a fun dining experience.
So if you find these guys in your lawn (and they like lawns a lot), enjoy their ambience but DON'T be tempted to save a few bucks on your grocery bill. If you do, it sounds like you'll be sorry.