This is somewhat of contradictory title, as Grass Pink Orchids (Calopogon tuberosus) normally have their flowers in varying shades of pink, often very vividly so. Every so often, an alba form can be found, but they are exceedingly rare. I have seen thousands of Grass Pink Orchids in my life, but only three that were ever white like this one.
Found blooming on a damp roadside in southeastern Orange County, Florida.