A picnic basket or picnic hamper was a type of basket used to carry food, drinks, and other items to a picnic.
A picnic basket was present when Christopher Pike and Vina had an illusory picnic in 2254. (TOS: "The Cage", "The Menagerie, Part II")
In 2269, a picnic basket was set on a blue blanket on the Shore Leave Planet for Hikaru Sulu, Leonard McCoy, the White Rabbit, Alice, and a two-headed dragon. (TAS: "Once Upon a Planet")
In 2369, Quark prepared a picnic basket for Lwaxana Troi and Odo, much to the latter's annoyance. (DS9: "The Forsaken")
While on the Caretaker's array in a recreation of a farmyard, some of the holograms brought picnic hampers with them while entertaining the crew of the USS Voyager. (VOY: "Caretaker")
During their shift into this dimension in 2371, a family on Meridian went out of their settlement for a picnic. The father carried a pincnic basket. (DS9: "Meridian")
Miles O'Brien brought one on the family's outing on Golana in 2374. (DS9: "Time's Orphan")
Seven of Nine also brought one to her and Chakotay's third date in 2378. (VOY: "Endgame")