The present study was undertaken to find the effect of genetic variants of beta-Ig on fat percentage, protein percentage, total solid percentage, casein percentage and 305 days milk yield in Red Sindhi cows. Red Sindhi animals (95) typed for beta-Ig variants (AA, AB and BB) by PAGE and PCR-RFLP, were screened for this study. Least-square analysis showed that all the 3 genetic variants AA, AB, and BB were having significant effect (P < 0.05) on fat percentage, protein percentage, casein percentage, total solids percentage and 305 days milk yield during different lactation periods and also having significant effect (P < 0.05) irrespective of lactation number. Genotype BB was having significantly higher fat percentage, total solids percentage and casein percentage than AA genotypes. Genotype AA was having higher protein percentage and higher 305 days milk yield than BB genotypes in the present study.