I’ve heard of other gatherings referred to as “bees” but I’ve always wondered why bees? If, by bee it is meant to draw the image of a group, wouldn’t Spelling Hive be more appropriate? What is the origin of the spelling bee and where was the first once held?
The 1769 cite was from Mathews, and refers to communal gatherings, not a spelling bee. The actual cite is “Last Thursday about Twenty young Ladies met at the House of Mr. Nehemian Liscome, here [Taunton, Mass.] on purpose fro a Spinning Match; (or what is call’d in the Country a Bee).”
Those country folks had obviously seen bees co-operate in a hive situation. The City folk called it a “Spinning Match.” No doubt they were more familiar with games/matches.
The first use of the word “hive” in reference to the phrases is from 1823, and said, in part "For the clergy, in country places,…they have what they denominate a ‘bee,’ or ‘hive.’ "
To the OP, the OED cites “spelling bee” from 1876.