From 1971 to 1982, he was President of Harlequin Enterprises Limited. In 1971 under Heisey's leadership Harlequin bought Mills & Boon a publisher of romance novels making Harlequin the largest publisher of Romance novels in the world. From 1982 to 1990 Heisey served as Chairman of Harlequin. Described as a "marketing genius", he revolutionised the sale and marketing of books in the international publishing industry. At Harlequin drawing upon his experiences at Procter & Gamble he first put free books in boxes of detergent and feminine sanitary napkins. Under his leadership Harlequin was the first publisher to sell books in drug stores and grocery stores. He pioneered the mail order book club and, contrary to publishing industry practise, refused to sell publishing rights to foreign publishing companies establishing new publishing ventures in new markets.