Coat 6-qt. slow cooker with cooking spray.
In medium bowl, stir together beef broth, red wine, flour, tomato paste and 1 Tbs. chopped thyme; reserve.
Season beef all over with salt and pepper. In large nonstick skillet, heat oil over medium-high heat. In batches, cook beef, flipping occasionally, until browned on all sides, about 5 min. per batch. Transfer to plate.
Place mushrooms, carrots and onion in bottom of slow cooker. Place beef on top of vegetables; add reserved broth mixture.
Cover; cook on low 8 hrs. Transfer stew to serving bowls. If desired, garnish with additional thyme.