Brown the ground beef in a medium sized pan. Cook until most of the pink is gone. Add the onion mushrooms and garlic and cook for an additional 3-5 minutes or until the onions are beginning to turn translucent. Transfer everything to slow cooker.
Add all of the ingredients to the slow cooker except the tortellini. If you want your soup to be thicker use 3-3 1/2 cups of broth. If you want it thinner use up to 4 cups of broth.
Cover and cook on high for 3-4 hours or low for 7-8 hours.
10-15 minutes before serving add the tortellini, cover and cook until the tortellini are soft (15-20 minutes for frozen tortellini).