Budgeted at around £100,000, the PR aim is to maximise public understanding of and involvement in the 2011 Census across Scotland.
The 2011 Census publicity campaign was tendered as part of the Scottish Government's central framework for the provision of marketing services.
The BIG Partnership senior account director Allan Buchan said he aimed to use the agency's knowledge of community engagement programmes to ensure the campaign achieved its objectives.
The BIG Partnership's appointment by GROS marks the latest contract win for its public sector division, formed recently to harness its specialist expertise in this area for existing and new clients. Account director Kim Munro is leading the new division.
Recent public sector wins for BIG include the Scottish Government's Know the Score drugs awareness campaign and Scotland's new skills body, Skills Development Scotland.