Aims: As conservation agriculture have been proposed as an option to limit conventional agriculture impact and to ensure sustainability and food security. This study examined the effect of conventional tillage (CT) and no tillage (NT) on mycorrhization rate, mineral elements uptake, total phenolic content (TPC) and total flavonoid content (TFC) of oat during tillering. Study Design: Split-plot design was applied for this study. Place and Duration of Study: The experiment was conducted at the referential farm for direct drilling (Krib, Siliana) situated in northwestern Tunisia during 2015/2016 cultivation year. Methodology: Mycorrhization rate (MR), mineral elements uptake, total phenolic content (TPC) and total flavonoid content (TFC) of oat were studied as affected by conventional tillage (CT) and no tillage (NT) during tillering stage. Results: The results showed that tillage practices (T) had no significant effect on mycorrhization rate, mineral uptake, total phenolic content and total flavonoids content under rainfed conditions. Even if NT had no significant effect on MR, higher rates were noted for NT compared to CT. Conclusion: This study extends our knowledge on oat mycorrhization, mineral elements uptake, TPC and TFC as affected by tillage practices to advance results helping decision makers for no tillage adoption upscaling in Tunisia under rainfed conditions.