<p>Today, consumers see food not just as a source of nourishment, but also as a means to prevent and control diseases. This study examines the production of gluten-free fermented beverages based on quinoa, oats, rice, and a combination of these grains (rice-quinoa, rice-oats, oats-quinoa, and rice-oats-quinoa in equal proportions) by the probiotic bacterium <i>Lactobacillus acidophilus</i>. The study evaluates the effects of raw material type and storage time on pH, acidity, dry matter, alcohol content, total phenols, DPPH free radical scavenging percentage, lactic acid viability, and overall acceptance during 14 days of storage of gluten-free fermented beverages. The results indicate that the rice sample had the highest pH (4.51) and <i>Lactobacillus acidophilus</i> (10.87 log CFU/mL) bacteria count, as well as the lowest acidity (1.60 ^°D) among the produced beverages, which was statistically significant compared to other samples (<i>p</i> &lt; 0.05). The highest percentage of DPPH free radical scavenging (53.25%), similar to phenolic compounds, was found in the fermented beverage made from a rice-oat-quinoa mixture on the first day of storage. With increasing storage time, the alcohol and dry matter content in gluten-free fermented beverages also increased, while pH, dry matter, phenolic compounds, DPPH free radical scavenging percentage, <i>Lactobacillus acidophilus</i> count, and overall acceptance decreased. Principal Component Analysis (PCA) identified three main components, with the first component (F1) being the most influential. Lactic acid bacteria count, pH, dry matter, and DPPH free radical scavenging were the key factors affecting the characteristics of the fermented beverages. Based on the results, it can be concluded that a probiotic drink based on a rice-oat-quinoa mixture could serve as a beneficial and healthier alternative to conventional market drinks.</p>