The £100,000 brief includes targeting lapsed and reduced users of the WeightWatchers from Heinz (WWfH) range, which includes oven-chips, curries and chocolate desserts.
Cow is charged with getting the brand mentioned in editorial features on slimming and relevant issues in national publications.
Heinz recently said it was to refocus and develop the WWfH range after speculation that it would sell off its frozen-food brands.
Cow won the brief after a four-way pitch. Shine Communications has worked previously on the WWfH brand, but only on projects, and did not pitch for the brief.
Shine and Grayling continue to work on other Heinz products. Heinz UK & Ireland director of corporate and government affairs Nigel Dickie said: ‘Despite this appointment, we will not be reviewing any of our other comms agencies.’
Cow director Clare Myddleton heads a three-strong agency team reporting to Heinz head of marketing, desserts and potatoes, Amanda Walker, and senior brand manager Petra Brundelius.
Cow this week appointed Karen Salem, who will work on the Heinz account, to the role of account manager.
Salem previously spent seven years at agency Manning Selvage & Lee.