It is the fourth year the picking crews have entered the vineyard early and Mr Wheeler said it was all about getting to the grapes before the sugar levels went up, as low sugar levels meant lower alcohol.
Winemaker Paul Mooney had been keeping a close eye, and taste, on the grapes and determined they were at the right stage for picking; not too ripe.
The Mission had developed what was effectively a trial run of low-alcohol pinot gris from the 2014 vintage and response to it had been good.
The first harvest of 2014 saw about seven tonnes of the organically grown pinot gris hand-picked but the following season saw that figure rise to about 20 tonnes.
Thursday's harvest saw about 30 tonnes picked from a section of the vineyard Mr Wheeler said had recovered back to full production.
Organic yields can fall away as less fertiliser and no herbicides are used, and using mechanical weed eaters can put some strain on the vines.
But using organic weed controls, Mr Wheeler said, they had managed to get the vines back to good production, and he said despite the bout of rain late last months it was all looking "pretty good" for the 2017 vintage.
"In fact the reds are looking fabulous," he said.
There had only been a small amount of splitting due to the rains and the long-range forecasts were looking to be in the grapes' favour.
The fermentation process will get under way immediately and bottling was likely to be a couple of months away.
Mr Wheeler said the low-alcohol market was relatively new and still regarded as something of a novelty, but it was a growing one.