The present study was designed to investigate the effects of co-supplementation of β-galacto-oligosaccharides (β-GOS), a prebiotic, and methionine on selected meat quality traits, and the pathways governing breast muscle formation and degradation in broilers. Day-old broilers (n = 288) were distributed in a 3×2 factorial design (6 groups and 6 replicates/group) based on three dietary levels of β-GOS (0, 0.2 and 0.5%) and two levels of methionine (0.5 and 1.0%). On day 35, two birds per replicate (12 birds per group) were exsanguinated to collect breast muscle samples for analysis. Results showed that β-GOS supplementation reduced the initial pH_15min (P<0.05), rate of pH change, cooking loss (P<0.05), and muscle fiber diameter (P<0.05) with a concomitant increase in the muscle catalase level (P<0.05), and fiber density (P<0.05). Methionine (1.0%) downregulated the expression of MAFbx (P<0.05) and MuRF1 (P<0.05) genes. Methionine (0.5%) supplementation significantly decreased the drip loss and upregulated the expression of MyoD (P<0.05) and M-CK (P<0.05) genes. We conclude that though β-GOS and methionine co-supplementation did not show any promising effects on meat quality in broilers, still, both β-GOS and methionine partially improved the selected breast meat traits (decreased pH_15min, ∆pH, elevated antioxidant activity, lower cooking loss, and higher muscle fiber density) and breast muscle degradative changes (downregulating the expressions of MuRF1 and MAFbx genes) respectively.