1. Brown the meat in a skillet over medium-high heat. (This gives the meat more flavor and helps it hold together better, but you can skip this step to save time.)
2. Place peas, carrots, celery, and barley on the bottom of a four-quart crock-pot, and place meat on top. Place mushrooms on top of the meat. Combine water and soup mix and pour over meat.
3. Cook on low for six to eight hours or on high for three to four hours. Serve with a tossed salad for a complete meal.