Dice the veggies into large chunks. If you'd like, leave the onions whole. Cut the top off a garlic head and leave it whole and unpeeled.
Rub the meat generously on all sides with salt and pepper. Brown the meat on all sides on a hot skillet.
Add the beef, carrots, onion, garlic, garlic powder, and a teaspoon of salt into the slow cooker.
Sauté the mushrooms over high heat and cook them until they turn golden brown on all sides. Pour in the wine and about one cups of hot water.
Cook the roast in the slow cooker for about 5 hours, or until the meat easily falls apart when flaked with a fork.
Remove the meat from the slow cooker. Spoon out the juice and mushrooms if you wish. Serve the beef in sandwiches, quesadillas, or over mashed potatoes.