The Meath golfer along with England’s James Ruebotham, Swede Rikard Karlberg and South African Jaco Van Zyl were disqualified for taking wrong drops at the 18th hole in Le Golf National near Paris.
All sent balls into the lake at the 18th and then played from the wrong spot after taking a penalty.
Because they left the recording area, unaware they had broken the rule, they were effectively disqualified for signing for a wrong score.
Players had been informed of the correct way to drop the ball at 18 in sheets handed to them before play and on notice-boards.
“One player said he had read the notice explaining how to drop the ball correctly but forgot it and the other three said they had not read the notice,” European Tour chief referee Andy McFee told reporters.
“This rule was in force last year and we didn’t have one disqualification. I’m bemused.”
McGrane held up his hands, saying: “I didn’t read the notices and my caddie misinterpreted them.”
It was the greatest mass disqualification since 1990 when six players were dumped out in the first round of the AGF Open at La Grand Motte, Montpellier, for removing out of bound posts — considered immovable objects — to play their shots.
Back on the course England’s Graeme Storm is tied in the lead with Australian left-hander Richard Green at six-under-par 65.
South African George Coetzee and Dane Thorbjorn Olesen are a shot further back.
Gareth Maybin is best of Irish five shots off the lead on one under with Paul McGinley on even par and Michael Hoey one over.
Peter Lawrie is tied 90th on two over with Darren Clarke three over while Shane Lowry will be lucky to make the cut on seven over.