Abstract: The present invention provides a process for preparing a pro-biotic oat-based fluid food product, the process comprising: A) a first fermentation step, involving the fermentation of oat material; B) mechanically treating one or more unfermented oat-derived substances in the presence of water to form an aqueous suspension containing 1,3-1,4 ? D-glucan in dissolved and/or suspended form, wherein the average molecular weight of the 1,3-1,4 ? D-glucan in the suspension is at least 1,500,000 Daltons, and combining the products from the first fermentation step with the one or more oat-derived substances and the water, before, during or after the formation of the aqueous suspension; and C) a second fermentation step, involving the fermentation of the aqueous suspension in the presence of Lactobacteria and/or Bifidobacteria, until the quantity of Lactobacteria is at least 10E7 CFU/g and/or the quantity of Bifidobacteria is at least 10E7 CFU/g.