The ceremony took place on August 5, which would have been her 11th birthday.
In early 2018, the then 8-year-old huntaway-Labrador cross, the beloved pet of Andy and Alison Cunningham, was the subject of an intensive five-week search by hundreds of volunteers.
Meg had suffered badly injured legs in a car accident and had gone to ground.
She was treated by the Wildlife Hospital Dunedin veterinary team Dr Lisa Argilla and Angelina Martelli, in their own time, before being transferred to her usual vet.
Her experiences were the subject of the book Remarkable Meg, written and illustrated by St Clair author Rachel McCoubrey.
The dog's health declined early this year, and she was euthanised on March 13.
Friday’s unveiling and "birthday party" was a chance to honour Meg’s legacy of hope, organiser Mandy Mayhem-Bullock said.
The plaque, designed by Meg Brasell-Jones, and funded with a $130 grant from Waikouaiti Community Board, would stand as an ongoing reminder to "never give up", she said.
Mr Cunningham said Meg had lived "an amazing life" and felt that what would have been her 11th birthday was "the right time to remember her with love".
He thanked everyone who had cared for her and all those involved in creating the memorial plaque.