The practice of a dinner and evening of entertainment goes back at least as far as the first known mention of the dinner in 1683. According to the Oxford English Dictionary (OED), Mechanick Exercises by Joseph Moxon describes the event as such:
"It is also customary for all the Journey-men to make every Year new Paper Windows...; Because that day they make them, the Master Printer gives them a Way-goose; that is, he makes them a good Feast, and not only entertains them at his own House, but besides, gives them Money to spend at the Ale-house or Tavern at Night. These Way-gooses, are always kept about Bartholomew-tide. And till the Master-Printer have given this Way-goose, the Journey-men do not use to Work by Candle Light."
"An annual outing and dinner of the staff of a printing works or the printers of a newspaper. Originally the word applied to a dinner given by a master printer for his workmen each year on or around St Bartholomew's Day (24 August)." (From Foyle's Philavery: A Treasury of Unusual Words, by Christopher Foyle.)