Gather all your fresh ingredients. Measure out the Dijon mustard, white grape juice, and olive oil.

In a bowl, combine the Dijon mustard, white grape juice, olive oil, minced garlic, chopped rosemary leaves, and black pepper. Whisk until smooth.

Coat each chicken breast in the marinade thoroughly. Refrigerate for at least 30 minutes.

Preheat your oven to 375°F (190°C). Let the marinated chicken rest at room temperature.

In an oven-safe skillet, heat the olive oil over medium heat. Sear each side of the chicken breasts for about 3 minutes.

Pour any remaining marinade over the seared chicken breasts and bake for approximately 30 minutes or until cooked through.

Let the chicken rest briefly before serving. Serve with sauce drizzled over top.