Into a slow cooker, put the onions, carrots, mushrooms, and potatoes.
Season the roast with salt and pepper. In a large skillet over medium-high heat, brown the meat on all sides in oil. When it is browned, put it in the slow cooker on top of the vegetables.
In a small bowl, stir together the cream of celery soup, onion soup mix, beef broth, and steak sauce. Pour over top of roast. Cover and cook on high setting for 3 to 4 hours or low for 8 to 9 hours.