A tray was a flat surface used to transport and serve food.
Trays were in use in the mess halls aboard Enterprise NX-01 and USS Voyager. (ENT: "The Andorian Incident", "Breaking the Ice", "Fortunate Son"; Star Trek: Voyager)
Chef used a tray to serve ration packs of pot roast while the crew was forced to stay in Enterprise's catwalk in 2152. (ENT: "The Catwalk")
Ensign Hoshi Sato used a tray to bring some food, including angel hair pasta, to sickbay in 2153. (ENT: "Regeneration")
In 2266, Janice Rand was accosted by the M-113 creature posing as Crewman Green as it attempted to get the salt off a tray of food she was carrying. Later, she delivered the meal to a very grateful Hikaru Sulu. (TOS: "The Man Trap")
Later that year, Lieutenant junior grade Joe Tormolen obtained a tray of food from a food synthesizer in a recreation room aboard the USS Enterprise. He placed the tray on one of the room's tables but an incident shortly thereafter, in which he accidentally stabbed himself with a knife from the tray, prevented him from eating the food on the tray. (TOS: "The Naked Time")
Kevin Riley's meal in engineering was also on a tray. (TOS: "The Conscience of the King ")
In 2267, Christine Chapel carried a bowl of plomeek soup to Spock on a tray. (TOS: "Amok Time") Later, she brought Ensign Garrovick a meal on a tray, in an attempt to coax him to eat something. (TOS: "Obsession")
The Ocampa used trays for carrying their food from the food dispensers. (VOY: "Caretaker")
In 2371, Neelix and Kes used trays to serve hors d'œuvre on the bridge. (VOY: "The Cloud")