This will be the first campaign of its kind by the Agency and follows a branding review by specialist shop Wolf Ollins.
A shortlist of five agencies has now been assembled, with pitches taking place on 10 February. An appointment is expected within weeks.
A spokesman said this is the first time the entire region, rather than its separate areas, has been promoted as a single brand. The focus will be on international and national media with key messages to promote the area to firms and tourists.
The agency covers the local authority areas of Gloucestershire, South Gloucestershire, Swindon and Wiltshire, Bristol, Bath & North East Somerset, North Somerset, Somerset, Bournemouth, Dorset and Poole, Devon, Torbay and Plymouth, Cornwall and the Isles of Scilly.