Manches is expanding its Oxford practice with a move to a new 40,000 sq ft office, nearly three times its current capacity in the city.
The firm hopes to finalise the negotiations in a matter of weeks, with the expectation that the office will be operational by early next year.
Manches' 48 fee earners in the region, who billed £6m in the last financial year, are spread across five offices with a total area of 16,000 sq ft.
The new office will provide space for Manches, whose leading clients include the University of Surrey and Brunel, to more than double its staff levels in the region.
The move is a mark of the growing importance of the Thames Valley region to commercial law firms, which are pitching to service start-up IT and biotech businesses connected to leading universities.
Recent weeks have seen US firm Brobeck Hale & Dorr hire three corporate partners from Morgan Cole to set up an Oxford base, the first time an established US firm has ventured outside London, while Osborne Clarke has just doubled its space at its Reading office.
Manches' Oxford head Peter Angel told Legal Week the firm was following a strategy of developing its client base in the region rather than expanding to other university towns such as Cambridge.
Angel added: "Cambridge is pretty heavily served at the moment, so we take the view that it makes more sense for us to grow our operation here."