The turkey producer called a review of its ad account, which was previously handled by Blac, back in February and selected Agency Insight to manage the pitch.
Isobel's first work for the brand is expected to break in the autumn.
Bernard Matthew's image has suffered recently following celebrity chef Jamie Oliver's attack on its Turkey Twizzler product range and a damaging outbreak of avian flu last year at its farm in Holton, Suffolk.
Following the outbreak, sales of its products dropped by 17% to £245m in the year to 22 April 2007, according to TNS Worldpanel.
Earlier this year, Bernard Matthews announced that by August all the turkey it uses in its products will be 100% British.
In addition this week it revealed it was overhauling its 'fresh added value' brand as part of a wide-ranging recovery plan.
The company has slimmed down its range of chilled breaded poultry products from 15 to eight variants, including Breaded Escalopes, Sauce Topped Escalopes, Crispy Steaks and Goujons.