Place first 4 ingredients in a 5-quart electric slow cooker; toss gently.
Heat oil in a large skillet over medium-high heat. Add beef to pan, browning on all sides (about 8 minutes). Place beef over vegetables in slow cooker. Coat skillet with cooking spray. Add onion to pan; sauté 5 minutes or until onion begins to brown. Stir in broth, scraping pan to loosen browned bits. Reduce heat; stir in mustard and next 5 ingredients. Pour broth mixture over beef and vegetables.
Cover and cook on LOW 8 hours or until beef and vegetables are very tender. Discard bay leaves. Garnish with thyme sprigs, if desired.
Young Chefs can:
Measure rutabaga, parsnip, carrot, and potato
Place rutabaga, parsnip, carrot, and potato in slow cooker