Details here of a Freedom of Information Request. If the information is accurate, then any and all inclusion of the "Big Society" were made no earlier than August 2010. This came several months after the last general election. The Conservative Party's campaign slogans included the "Big Society" and this party formed the majority of a new coalition government.
Furthermore, if the information is accurate, the AHRC included the "Big Society" with increasing frequency. The documents state:
"[. . .] We have found that subsequent versions of the document contained 1, 3, 5, 7, and 8 references to the term “Big Society”, with the published version decreasing to 5 references. These versions of the plan were circulated internally by the AHRC’s Chief Executive Officer (CEO) to members of the Senior Management Team, AHRC’s Council members and Chairman for comments and further iteration. Drafts of the Delivery Plan were also discussed with the Department for Business, Innovation and Skills (BIS) and circulated within Research Councils UK (RCUK). [. . .]"
There was a further request made to publish previous draft copies of the delivery plan. The AHRC have not released these documents.
The evidence suggests, if accurate, that there was no engagement with "stakeholders" (if understood as academics not part of the management structure or relevant ministers) in considering whether to include the "Big Society" in the delivery plan.
UPDATE: Readers may also be interested in this link.