Finnish celiac disease and dermatitis herpetiformis patients have used oat-containing gluten-free diets since 1997. The aim of this study was to evaluate how the use of oats has been adopted. The use of oats and the effect of oats on symptoms and quality of life were investigated in 1,000 randomly selected members of the Celiac Society. Altogether, 710 patients responded: 423 (73%) with celiac disease and 70 (55%) with dermatitis herpetiformis were currently consuming oats. Patients appreciated the taste, the ease of use, and the low costs; 94% believed that oats diversified the gluten-free diet; 15% of celiac disease and 28% of dermatitis herpetiformis patients had stopped eating oats. The most common reasons for avoiding oats were fear of adverse effects or contamination. There is a market demand for oats, and celiac societies and dietitians should make efforts to promote the development of products free of wheat contamination.