The pubs are across Cornwall, Devon and Somerset and including the Rolle Quay in Barnstaple, the White Hart in Launceston and the Four Lords in Par.
Red Oak owns more than 200 pubs, which are largely leased and tenanted, focused in the midlands, south, north west and south east of England.
Chief executive Mark Grunnell said he was delighted St Austell chose to work with the business in selling the assets.
He added: “We’re committed to the continued growth of our pub portfolio and this package of acquisitions will further strengthen Red Oak’s presence in the south west region.
“It is important to us we ensure ongoing consistency for pub guests and our new tenants and I would like to thank Kevin and the team at St Austell Brewery for working positively with us to effect a smooth transfer for these community assets.
“We are looking forward to working in partnership with all 17 of our new licensees in this new exciting chapter, providing ongoing support to help their businesses thrive.”
St Austell Brewery is an independent family business and owns 184 pubs and hotels across the West Country including managed houses and leased and tenanted sites.
Last month (September), it acquired four-site strong Bath Company for an undisclosed sum.
Red Oak is a committed and respected operator, with a growing pub estate and strong track record of running successful wet-led community pubs, according to St Austell Brewery chief executive Kevin Georgel.
He said: “We’ve been working very closely with the team in the past couple of weeks to ensure a smooth transition for our licensees.
“Unlocking the full potential of our pub estate is a priority for us as we continue to develop our business for the future.
“As part of our commitment to ongoing investment and growth, we are continuing to proactively manage our estate, aligned to our refreshed and focused strategy.
“This means ensuring all our pubs have a strong alignment with our long-term plans and continue to fit our focus in terms of market and consumer positioning.”
Georgel outlined how St Austell as a business committed to supporting its tenanted partners and investing in its estate, was confident Red Oak was the best custodian for the pubs and would ensure their ongoing success.