Which herb is frequently substituted for thyme in ratatouille?

Thyme is a classic herb in ratatouille, known for its earthy and slightly minty flavor that complements the other ingredients beautifully. Rosemary is frequently substituted for thyme due to its robust flavor profile, which can stand up to the heartiness of the vegetables in ratatouille. While rosemary brings a piney aroma and a distinct taste, it also aligns well with the Mediterranean roots of ratatouille, harmonizing with the other herbs typically used in this dish.

Other herbs like chives and sage do not closely mimic the flavor characteristics of thyme. Chives have a mild onion flavor that may not provide the depth needed, while sage's strong and distinctive flavor could overwhelm the dish. Marjoram is similar to thyme but does not offer the same depth of flavor and may not provide the desired complexity when used in ratatouille. Hence, rosemary makes a fitting substitute, as it complements and enhances the overall dish while maintaining its essence.