I agree in that it would probably like to be mounted, if you can meet it's other requirements. I am a big proponent of mounting epiphytic orchids in general as I feel they do best that way.
There's a catch though.
Mounted orchids, outside tropical and semi-tropical areas (and even then, not always), are not for the forgetful waterer or really those that don't have time to devote to monitoring a plant daily. This is especially true for plants, like Oncidiums, that like to stay moist all the time.
However, mounts are really quite spectacular if you like to do "something" with your plants all the time... think the chronic over-waterer. A few orchids aside, it is nearly impossible to over-water a mounted plant.
Now, you can really mount on a variety of things. For this plant, since it likes to stay moist, I would recommend Kool-Logs
or - Terracotta Mounting Jars #
. Sometimes you can get lucky and find unglazed pottery at craft stores and such, and that would work as well. Unglazed clay containers filled with water weep and keep the outer surface moist. That is, anyway, until the water is gone. I need to fill my Kool-logs daily to every other day, depending on the size, how warm it is and how much humidity there is.
You could probably also use regularly mounting media, like cork bark, driftwood or other types of wood. Make sure you use a pad of moss to help keep moisture and be prepared to water everyday, even multiple times per day if necessary.