Five different cooking methods - blanching, boiling, steaming, sautéing and high temperature (121°C) cooking - were applied to Ocimum herbs. Four Ocimum species - O. americanum (hairy basil), O. tenuiflorum (holy basil; syn. O. sanctum), O. basilicum (sweet basil) and O. gratissimum (wild basil) - were used to determine the effect of heating on their antioxidant capacity, total phenolic content, and presence of phytochemicals. Cooking with excess water, blanching, and boiling resulted in a reduction in both antioxidant capacity and phenolic content. HPLC chromatograms revealed that rosmarinic acid leached from the sweet basil leaves into the cooking water, in which sinapic acid was also detected. Meanwhile sautéing, as well as steaming at atmospheric and high pressures respectively, generally enhanced the antioxidant capacity of Ocimum, which was related to an increase in phenolic content. Similar chromatograms were detected in fresh, atmospheric steamed, and sautéed leaves, although the intensity varied. A major compound of the studied Ocimum herbs, rosmarinic acid, although found to increase in sautéed leaves, was substantially minimized in leaves steamed under pressure.