Background: It is well established that consuming ≥3g high-molecular-weight (MW) oat β-glucan (OBG) reduces low-density-lipoprotein-cholesterol (LDL-C). However, the effect of OBG on LDL-C in people with an LDL-C <160 mg/dL, is not clear.Objective: To determine the effect of OBG on LDL-C in people with LDL-C <160 mg/dL. Method: We reanalyzed the results of a previously published randomized, controlled, double- blind clinical trial on the effect on LDL-C of consuming breakfast cereal containing 3g high-MW (3H), 4g medium-MW (4M), 3g medium-MW (3M), 4g low-MW (4L) OBG or a wheat-bran control (W) for 4-weeks. We included only the 247 (67%) of the 367 subjects with LDL-C <160 mg/dL at screening. Changes in LDL-C from 0- to 4-weeks on each treatment were analyzed by one-way ANOVA and individual means compared by Tukey’s test (2-tailed t<0.05) to adjust for multiple comparisons. OBG viscosity was measured after simulated digestion in an in-vitro system. Results: On W, 3H, 4M, 3M and 4L, respectively, LDL-C changed by (mean±SEM) +2.1±1.9, -8.1±2.1, -8.9±3.0, -4.8±2.9 and -1.0±2.6 mg/dL; the changes on 3H (MW=2,2000,000 g/mol) and 4M (MW=850,000 g/mol) differed significantly from that on W; the changes on 3M (MW=530,000 g/mol) and 4L (MW=210,000 g/mol) were not significant. Mean changes in LDL-C were negatively related to log (viscosity) (p=0.015). Conclusion: Consuming 3g oat β-glucan is effective in reducing LDL-C in people with healthy LDL-C levels, but a MW of at least 850,000 g/mol is required for an optimal effect.