This study aims to optimize the fermentation process of purple onion to develop a probiotic-rich feed supplement for poultry. Fermentation was conducted under varying conditions, including temperature, salt concentration, and the use of lactic acid bacteria derived from indigenous microbial communities, mixed starter cultures, and commercial starters. Results indicated that a temperature of 29°C was optimal for fermentation, promoting faster pH reduction and acid production compared to 18°C. Lower salt concentrations (2%) accelerated the fermentation process, while both mixed and commercial starter cultures facilitated a more rapid decrease in pH to 3.5 within a shorter timeframe. These findings provide valuable insights for improving the production of fermented onion-based probiotics, contributing to reduced antibiotic use in poultry farming.