The objective of the research study was to produce oat breads, containing a high amount of wholemeal oat flour and showing a proper sensory quality, by means of applying some selected starter cultures. Eleven strains of lactic acid bacteria (LAB), occurring naturally in organic wholemeal oat flour, were isolated. Among the isolated strains, six strains belonged to Lactobacillus plantarum species, two strains to Pediococcus acidilactici, two strains to Pediococcus pentosaceus, and one strain belonged to Leuconostoc mesenteroides species. The suitability of the isolated LAB for making baker’s starter cultures was determined based on the results of assessing the following: capability of growing at various temperatures, quantity of synthesized lactic acid and acetic acid, and individual ability of each LAB strain to modify the fermentation process and to positively impact sensory qualities of sourdough. From among the LAB strains selected, three mixed starter cultures were prepared; they varied in the number of strains and in the strain composition. A mixed starter culture, characterized by the capability of inhibiting mould growth in oat sourdough, was added to the baked experimental products; this started culture consisted of: L. plantarum KKP 1797, L. plantarum KKP 1803, P. pentosaceus KKP 1804, P. acidilactici KKP 1805, and L. mesenteroides KKP 1807. Four experimental variants of wheat-oats bread were prepared using the sourdough produced with the application of the starter culture made; the sourdoughs used to make the four bread variants differed in the content of wholemeal oat flour. The bread containing 30 % of wholemeal oat flour in the sourdough was characterized by such a volume and sensory quality that it was possible to classify it into the first quality class according to PN-A-74108:1996.