In a small bowl, combine rosemary, salt pepper and garlic. Rub over tenderloin.

Pour 1/2 cup of water in the slow cooker and add the tenderloin. Cook on low for 5-6 hours.

While tenderloin is cooking, in a small pan whisk together brown sugar, cornstarch balsamic vinegar, water and soy sauce. Heat over medium and stir until mixture thickens, about 4 minutes. Add blueberries and simmer until warm, about 2 minutes.

When tenderloin is done, remove from slow cooker and let rest 5 minutes. Drizzle glaze over tenderloin.

Slice and serve.