The paper presents the results of a research into the apparent viscosity of flour water slurries of whole oat flour. The whole oat flours were produced by grinding 6 oat varieties showing a different content of dietary fibre and its components, especially of the soluble dietary fraction (SDF) including (1-3) (1-4) β-D glucans. 10 and 15 % oat flour slurries were rheologically analysed; after the time-varying stabilization of slurries (0.5 – 2 h), the measurements were taken; the shear rate gradient varied (200-1200 s^-1). The apparent viscosity was measured using a spindle-type rotational rheometer with coaxial cylinders, i.e. a RM 180 Mettler Rheomat model. It was found that the apparent viscosity of oat flour water slurries analyzed was instable during the stabilization (0.5 – 2 h). A significant increase in the viscosity occurred along with the elapsing of the stabilization time of slurries. It was proved that the impact of shear rate gradient on the apparent viscosity changed and depended on the stabilization time applied. The correlation (Pearson, p ≤ 0.05) between the content of individual dietary fibre fractions and the apparent viscosity of slurries was analyzed and it was proved that the viscosity of slurries was correlated, to the highest degree, with the content of (1-3) (1-4) β-D-glucans.