The jobs of the 67 Tuffins employees at the Lydney and Coleford stores have been secured, along with the 382 at its other branches, says the Co-op. Some 39 people work at Lydney, with 28 at Coleford.
Midcounties will purchase the family-owned chain of sites in Powys, Flintshire, Shropshire and Gloucestershire to grow its estate within its trading heartland.
"Midcounties is keen to build on the success enjoyed by Harry Tuffins with a key focus on maintaining the strong community associations the independent retailer has built over the past 50 years," states the Co-op.
Midcounties chief executive Ben Reid said: "As a member-owned society with values of democracy, openness, equality and social responsibility, we believe the fairer way we do business is an excellent match with the family ethos the company has long adhered to."
He said the stores, including those in Lydney and Coleford, where the Society already has branches, will continue to trade as Harry Tuffins.
"The Harry Tuffins outlets carry large numbers of non-food items, while the Co-operative stores are primarily food, so they are complementary and can trade happily together," he said.
"We will, over time, take the opportunity to update the shopping experience but customers and our new colleagues can rest assured we fully appreciate how much this unique group of stores are cherished by their local communities."
Harry Tuffins' owners, the Delves family said: "We are confident that in The Midcounties Co-operative we have found someone who shares our values and understands these stores have a special place in the community, and they will continue that tradition."