Macgregor will take to the water off the coast of The Hague with Tom Phipps as those sailors across the globe tackling the new Olympic class for Rio 2016 descend on the Netherlands.
Macgregor, who skippered the British match racing team that finished seventh at the London 2012 Olympics last summer, and Phipps are one of four British crews in action off Scheveningen.
Transferring to the Nacra 17 after women's match racing was dropped from the Olympic programme, Macgregor joins Pippa Wilson, a Yngling gold medallist from Beijing 2008, and her partner John Gimson.
Sail for Gold Regatta winners Ben Saxton and Hannah Diamond and Rupert White and Nikki Boniface complete the British quartet of pairs with 66 compulsory male and female crews in total.
Macgregor and Phipps are currently placed second in the ISAF world rankings in the inaugural Nacra 17 season but the former admits she really doesn't know what to expect in the Netherlands.
"It's a big event for us for sure. It's our biggest event of the year and one that we really want to perform in and to sail the best we can," said Macgregor.
"In terms of where that will be overall in the fleet, it's impossible to tell in some ways. Half of the fleet that will be there we won't have seen before.
"But that doesn't mean to say they won't be any good. It's very hard to say in advance that we want to be top five or top ten, or top twenty or whatever, because we don't really know what to expect.
"Within our team we know how we can sail, and so I think although it sounds a bit clichéd, Tom and I have really just got to focus on that, do the best we can do and see where that puts us overall ultimately."
Meanwhile Britain's Finn sailors are in continental action at the European Championships in Germany with Mark Andrews, Andrew Mills and Ed Wright all taking to the water.
And Andrews, who has won the past three EUROSAF Champions Sailing Cup regattas in Holland, Kiel and on home waters in Weymouth, believes he's peaking at the right time.
"I'm definitely getting better and better as the year goes on and it's nice to be peaking just in time for the two key events of the year, the Europeans and worlds," said Andrews.
"There have been a few people missing from the events so I wouldn't count my chickens too much, but you can only beat the people who turn up to the regattas and to have won three golds in a row is pretty good."