On a trip to Europe in the 1950s, Rudkin discovered fancy chocolate cookies that she believed would be popular in the United States. She bought the rights to produce and sell them, and the Distinctive Cookies line was born. Under her management, Pepperidge Farm continued to expand into other products, including frozen pastry items and, later, the Goldfish snack cracker from Switzerland. In 1961, she sold the business to the Campbell Soup Company for $28 million and became the first woman to serve on its board of directors. She drew on her knowledge and experience to write "The Margaret Rudkin Pepperidge Farm Cookbook" in 1963, which was the first cookbook ever to make the "New York Times" Best Seller list.