Have one and need to know a bit more about the culture for this orchid. It is mounted and mature size. lots of roots that all seem dry - no new growth. Let dry out in winter??
Oncidium cebolleta needs lots of water and light when it is in active growth but when it is in the state yours is in then it is ok to keep it dry just don’t let it get too shriveled. Other than that I can't be too much help.
I got this orchid from Andy's orchids . - love his orchids...it was blooming size when I got it in June. It put out a new 18 inch terrete leaf through summer then found new spike one week ago . Spike grew 2 inches in past 2 days. Keeping dry until blooms then will mist occasionally this winter. Thanks for all the information ...I couldn't find much on it before to go by..will send a pic when it opens (cross my fingers).