A picnic was an outdoor meal.
The Fourth Doctor and Leela freed several Zygon prisoners whilst on a picnic on Shontaa. (COMIC: Rest and Re-Creation)
When Sharaz Jek proposed him and Peri Brown to become his best companions, the Fifth Doctor mocked him about having picnics together. (TV: The Caves of Androzani)
Gilia encountered the Ninth Doctor as a child, while on a picnic with her parents and older sister. (PROSE: The Beast of Babylon)
Before they were married, the Tenth Doctor went on a picnic with Elizabeth I. (TV: The Day of the Doctor)
On 22 April 2011, the Eleventh Doctor had a picnic next to Lake Silencio with Amy Pond, Rory Williams and River Song. (TV: The Impossible Astronaut)
The Twelfth Doctor told Clara Oswald he had once had a picnic on Thedion Four, but had to wear a gas mask due to the planet's constant acid rain. (TV: Mummy on the Orient Express)
River Song and a Doctor shared a picnic at Asgard. (TV: Silence in the Library)