The effects of five processing forms on the content of phenolic compounds, antioxidant capacity, and saponin content in quinoa grains were evaluated. The processes included washing, washing followed by hydration, cooking (with or without pressure), and toasting. The highest content of phenolic compounds was obtained after cooking under pressure; however, these compounds also increased with grain washing. The toasting process caused the greatest loss. The antioxidant capacity of the grains was similarly affected by the processing techniques. According to the amount of saponins, the grains were classified as bitter. Washing caused a reduction in these compounds, but the levels remained unchanged after cooking (with and without) pressure and toasting; however, they significantly increased after hydration. Cooking, especially with pressure, had greater effects than the other processes, and potentiated the functional properties of quinoa grains.