Functional foods targeting the improvement of gastrointestinal health are widely recognized; of these, dairy-based probiotics are the most popular. Thus, the design of nondairy probiotics applying fruits, vegetables and cereals has raised great interest in the healthy food sector. The objective of this work was to assess the potential of germinated and malted oat substrates to support the growth of the probiotic cultures Lactobacillus acidophilus, Lactobacillus casei and Lactobacillus rhamnosus. Fermentations were carried out with distinctive oat substrates at inoculum levels of 3, 5 and 7% v/v, substrate concentrations of 3, 5 and 7% w/v and with sucrose addition 1·5% w/v. Lag phase profiles, maximum growth rates and maximal growths were evaluated; protein and sugar contents were also quantified. There was no significant effect (P > 0·05) of the inoculum size on the fermentation kinetics; however, oat media significantly affected the growth kinetics. In simple oat media, Lact. acidophilus exhibited biphasic growth patterns. Lactobacillus growth patterns were significantly affected (P < 0·05) by the supplementation with protein sources. The germination and malting processes significantly improved oats nutrient characteristics demonstrating to be adequate substrates for the fermentation with probiotic lactobacilli. Significance and impact of the study: In this work, the effect of oat media composition and fermentation conditions on the growth kinetics of three probiotic lactobacilli was determined. The variation in the inoculum levels did not have a significant effect on the probiotic cultures growth. Results revealed that protein supplemented simple, germinated and malted oat enhanced the cell viability of the probiotic lactobacilli; Lactobacillus casei exhibited better growth adaptability. The results also highlight that different weight in volume oat substrate concentrations has particular effects on Lact. casei growth kinetics. Our results contribute to a better understanding of oat-based media formulations as substrates for probiotic cultures.