TLG, using Populus' Opinion Leader Network panel, quizzed top business people, academics, journalists and politicians on the winners and losers of the 2012 Games.
The respondents said that BT's provision of telecoms services and infrastructure was the most valuable corporate contribution to creating a positive Games.
During the Games, BT provided 80,000 voice and data outlets, 16,500 fixed telephone lines, 14,000 mobile SIM cards and 1,000 wireless access points and supported the London 2012 Games website, which notched up an estimated 12 billion page views.
Further corporate contributions cited by 'opinion leaders' were Omega, for providing timekeeping, and GSK, in third place, for providing anti-doping facilities.
Respondents said Adidas had experienced the greatest positive change to reputation as a result of its Olympic sponsorship, followed by BT and BMW. In terms of the reputation of worldwide partners, Samsung received the greatest boost, followed by McDonald's and Omega.
The research also asked the panel about the importance of legacy from the Olympics. The top change that would represent a positive corporate legacy was seen as the successful regeneration of east London. The benefits of investment in the area outweighed legacies surrounding a healthier country and any resultant boost to UK tourism.
TLG managing partner Malcolm Gooderham said: 'Now the real comms challenge begins, transforming the legacy into competitive advantage, involving a further investment of time, money and thought leadership.'
The research also pulled out key lessons for the organisers of Rio 2016 - with the primary factor for future Games organisers to take on board being a fairer ticketing system for the public.