A high nutritional value of oat flour constituting a by-product derived from manufacturing a BETAVEN β-D-glucan concentrate suggested that the oat flour could be used as an addition in wheat and wheat-rye breads. The objective of the research project was to develop a recipe of wheat and mixed breads, where a portion of wheat flour was substituted with the leftover oat flour amounting to 10 %, 20 %, and 25 % of the wheat flour content. Another objective was to determine the impact of the oat flour used on the sensory and nutritional properties of the products manufactured. The results obtained show that the leftover oat flour is a good source of protein with a beneficial amino-acids composition, dietary fibre, and crude lipids, and its amount not exceeding 20% of wheat flour is fit for use as a supplement in wheat and wheat-rye white breads.