The assignment also includes the launch of an as-yet-undisclosed new product.
Saatchis claimed this week it was splitting with Burton's, whose product portfolio also includes Wagon Wheels, because of the company's decision not to have an agency of record but instead to award assignments on a project-by-project basis.
The change in agency arrangements has been led by Jaspal Chada, who took over as the marketing director at Burton's in February, having worked for Premier Foods and New Zealand Milk.
The Burton's account has been largely dormant for about two years. Before that, Saatchis produced TV work for each of the three brands.
Chada claimed Burton's portfolio had "huge untapped potential" and cited FCB's "energy, imagination and creativity" as the reason for the appointment.
Burton's is owned by the Texas-based venture capitalist Hicks Muse Tate & Furst, whose Weetabix subsidiary is an existing FCB client.
Kevin Dundas, the Saatchis chief executive, commented: "Burton's has decided to go on to a project-by-project basis and not to have an agency of record. Because of changes in the distribution of its brands and the management of those brands, it's a relationship that will not continue. We were proud of our work. But the brief is very different now from what it was then and we wish Burton's well."