Extruded breakfast cereals (EBC), processed from two oat lines, N979-5-2-4 (N979) and “Jim”, with β-glucan concentrations of 8.7 and 4.9%, respectively, were used to determine the impact of dry solids (DS) and bile acid (BA) concentrations on in vitro BA binding efficiency. A full fractional factorial design with levels for BA concentrations of 0.20, 0.47, 0.95, 2.37, and 4.73 μmol/g of total EBC slurry and for DS in the slurries of 0.8, 2, 3, and 4% (w/w) was selected. The absolute amount of BA bound (μmol) was measured for each trial in the experiment design. The percentage (%) of BA bound based on the total amount of BA added and BA bound per gram of DS of the EBC (μmol/g) were also presented and discussed. N979 in vitro digestion slurries had greater BA binding (μmol) than Jim slurries at different DS and BA concentrations, with greater differences at DS of 3% or above and at BA concentrations of 2.37 μmol/g or above. No difference in the absolute amount of BA bound (μmol) and percentage (%) BA bound occurred between the EBC slurries made from the two oat types at the lowest DS of 0.8% or the lowest BA concentration of 0.20 μmol/g. The efficiency of BA binding by β-glucan in these two EBC became more distinguishable at 3% DS or above and BA concentrations of 2.37 μmol/g or above, indicating that these two conditions can be employed to measure BA capacities for similar foods. Also, the β-glucan in the EBC produced from the N979 oat line was more soluble than that from the EBC produced from the Jim oat line. Thus, greater BA binding capacity may have been caused by both a greater amount of β-glucan and a greater solubility of β-glucan in N979 than in Jim EBC.