This study investigates the effects of oat beta-glucan on metabolic dysfunction-associated steatotic liver disease (MASLD) and its impact on gut microbiota and fibrosis development. Oat beta-glucan, a non-digestible polysaccharide, has shown potential therapeutic effects on hyperlipidemia associated with MASLD, but its impact on gut microbiota and fibrosis remains unclear. The researchers used a western-style diet (WSD)-induced model of MASLD and assessed the effects of beta-glucan supplementation on early and advanced liver disease. They found that oat beta-glucan supplementation did not affect body weight gain or glucose intolerance but significantly reduced inflammation and fibrosis in the liver. Mechanistically, this protective effect was not mediated by changes in bile acid composition or signaling but was dependent on gut microbiota and was lost upon broad-spectrum antibiotic treatment. Specifically, oat beta-glucan partially reversed unfavorable changes in gut microbiota, leading to an expansion of protective taxa, including *Ruminococcus* and *Lactobacillus*, and reduced translocation of Toll-like receptor ligands. The findings suggest that oat beta-glucan may be a cost-effective and well-tolerated approach to prevent MASLD progression and warrant further clinical studies.This study investigates the effects of oat beta-glucan on metabolic dysfunction-associated steatotic liver disease (MASLD) and its impact on gut microbiota and fibrosis development. Oat beta-glucan, a non-digestible polysaccharide, has shown potential therapeutic effects on hyperlipidemia associated with MASLD, but its impact on gut microbiota and fibrosis remains unclear. The researchers used a western-style diet (WSD)-induced model of MASLD and assessed the effects of beta-glucan supplementation on early and advanced liver disease. They found that oat beta-glucan supplementation did not affect body weight gain or glucose intolerance but significantly reduced inflammation and fibrosis in the liver. Mechanistically, this protective effect was not mediated by changes in bile acid composition or signaling but was dependent on gut microbiota and was lost upon broad-spectrum antibiotic treatment. Specifically, oat beta-glucan partially reversed unfavorable changes in gut microbiota, leading to an expansion of protective taxa, including *Ruminococcus* and *Lactobacillus*, and reduced translocation of Toll-like receptor ligands. The findings suggest that oat beta-glucan may be a cost-effective and well-tolerated approach to prevent MASLD progression and warrant further clinical studies.