Light: Most Oncidium can thrive in bright to nearly full direct sun depending on the species."Mule Ear" or Oncidium with thicker leaves can tolerate the higher direct light levels forseveral hours per day.
East, West or Southern facing windows will provide the ideal light conditions for home growers. Most home growers have also had a tremendous amount of success under lights.
Temperatures: Oncidium are generally intermediate to high growers. 55 to 65 F at night, and 75 to 85 F during the day. If humidity and sufficient air flow are provided, Temperatures up to 95 to 100 F are tolerated.
Water: Once to twice per week depending on your growing conditions. Generally, plants with fleshy large roots or leaves need less-frequent watering than thin-leaved or thin-rooted plants. Please keep in mind that some species may have natural conditions that require a winters rest which means less watering.
Humidity should be between 30 and 60 percent. Many oncidiums require less humidity than other orchids.
Potting As a general rule. the finer the roots the finer-grade potting should be used while large rooted plants prefer coarser mixes/medium grade. When repotting any oncidium, please position the plant in the pot so that the newest growth is farthest away from the edge. This will allows the maximum number of new growths before crowding the pot and needing to repot again. Repotting can be stressful on a plant and will require time to adapt. So Keep humidity high and the potting medium dry until new roots form.