One assumes that the Boston Tea Party was organized in advance as a contingency measure if more law-abiding petitions and protests failed, presumably by the Sons of Liberty, led by Sam Adams.

This website: http://www.bostonteapartyship.com/sons-of-liberty states it as a fact.

As far as I know, however, there is no historical account verifying this.

To get something like 100 men prepared with the wherewithal to dress up as Indians, and descend on the tea ships, must have taken some organization.

http://www.revolutionary-war.net/boston-tea-party.html

Many thought that when Sam Adams stood up at the public protest meeting in the Old South Meeting House (after the assembly had been told that Governor Hutchinson had refused to let the ships leave to take their tea back to England), and said, “This meeting can do nothing further to save the country,” this was the signal for the tea party to begin.

Exactly how or when it was organized, however, is unclear. Participant accounts do not illuminate the planning. Joshua Wyeth, who was 16 when he took part in the Tea Party said,

“I had but a few hours warning of what was intended to be done… To prevent discovery we agreed to wear ragged clothes and disfigure ourselves, dressing to resemble Indians… Our most intimate friends among the spectators had not the least knowledge of us… At the appointed hour, we met in an old building at… the wharf, and fell in one after another, as if by accident, as not to excite suspicion.”

http://www.boston-tea-party.org/account-Joshua-Wyeth.html

So he claims to have had a few hours warning, but does not mention who gave him the warning and the instructions.

George Hewes reports,

“When the committee returned and informed the meeting of the absence of the Governor, there was a confused murmur among the members, and the meeting was immediately dissolved, many of them crying out, "Let every man do his duty, and be true to his country"; and there was a general huzza for Griffin's wharf. It was now evening, and I immediately dressed myself in the costume of an Indian, equipped with a small hatchet, which I and my associates denominated the tomahawk, with which, and a club, after having painted my face and hands with coal dust in the shop of a blacksmith, I repaired to Griffin's wharf, where the ships lay that contained the tea. When I first appeared in the street after being thus disguised, I fell in with many who were dressed, equipped and painted as I was, and who fell in with me and marched in order to the place of our destination.

When we arrived at the wharf, there were three of our number who assumed an authority to direct our operations, to which we readily submitted. They divided us into three parties, for the purpose of boarding the three ships which contained the tea at the same time. The name of him who commanded the division to which I was assigned was Leonard Pitt. The names of the other commanders I never knew.”

http://www.boston-tea-party.org/account-george-hewes.html

George Hewes knew that he had to dress as an Indian, and there were commanders on the wharf, but how this was organized he does not discuss.

David Kinnison, who was a member of the Lebanon Maine Committee of Correspondance (groups formed to co-ordinate anti-British protest across the colonies) was in Boston. In an interview his is paraphrased as:

” They (meaning David himself and some of his friends) repaired to Boston, where they were joined by others; and twenty-four, disguised as Indians, hastened on board, twelve armed with muskets and bayonets, the rest with tomahawks and clubs, having first agreed, whatever might be the result, to stand by each other to the last, and that the first man who faltered should be knocked on the head and thrown over the tea.”

http://www.boston-tea-party.org/account-kinnison.html

Samuel Cooper, who was 16 and an eyewitness wrote.

“A little before sundown an alarm was created among the assembled citizens by the cry of fire, which was suppose to be given by some of the British officers who had attended the meeting in citizen dress and had given the alarm for the purpose of breaking up the assembly. They had nearly effected this object when the town clerk, Wm. Cooper rose and in a loud voice told the citizens that there was no fire to be apprehended but the fire of the British and begged them to keep their places.

Immediately after a detach’t of about 20 men disguised as Indians was seen to approach in single file by the west door of the Church. They marched with silent steps down the isle and so passed by the south door brandishing their tommahaws [tomahawks] in that direction. The appearance of these men created some sensation. No one appeared to expect their arrival and the object of their visit seemed wholly inexplicable. On leaving the church, they proceeded in the same order in which they entered it, down Milk Street through that part of town which led to Gray’s and Tiletson’s wharves where the tea ships lay.

Arrived at the wharves they divided into three troops each with a leader gained possession of the ships quietly and proceeded to lighten them of their cargo by hoisting out the boxes and emptying their contents into the dock. No noise was heard except the occasional clink of the hatchet in opening the boxes and the whole business was performed with so much expedition that before 10 o’clock that night the entire cargo of the three vessels were deposited in the docks.”

http://www.boston-tea-party.org/account-Samuel-Cooper.html

John Andrews, who was an eyewitness, reported,

“The house was so crowded that I could get no further than the porch. I found the moderator was just declaring the meeting to be dissolved. This caused another general shout out-doors and inside, and three cheers.

What with that and the consequent noise of breaking up the meeting, you'd have thought the inhabitants of the infernal regions had broken loose. For my part I went contentedly home and finished my tea, but was soon informed what was going forward. As I could not believe it without seeing for myself, I went out and was satisfied. The Indians mustered, I'm told, upon Fort Hill, to the number of about two hundred, and proceeded, two by two, to Griffin’s wharf, where Hall, Bruce, and Coffin's vessels lay. Coffin's ship had arrived at the wharf only the day before, and was freighted with a large quantity of other goods, which they took the greatest care not to injure in the least.

Before nine o'clock in the evening every chest on board the three vessels was knocked to pieces and flung over the sides. They say the actors were Indians from Narragansett. Whether they were or not, to a transient observer they appeared such.”

http://www.boston-tea-party.org/account-john-andrews.html

So, there is some evidence that some participants had at least a few hours warning. The participants knew to dress up as Indians, and had time to prepare costumes. There was organization on the wharf, but exactly when this was planned and organized, and by whom, has not (as far as I know) ever been revealed.