Heat oil in a large Dutch oven over medium heat. Add onion; cook 3 minutes or until slightly soft. Add sausage links to pan; cook 12 - 14 minutes or until sausage is browned and almost cooked through.
Remove sausage links to cutting board and allow them to cool before coin slicing. Stir in carrots, parsnips, mushrooms, celery and Swiss chard into the Dutch oven. Add the barley, tomatoes, stock, wine, Italian seasoning, salt and pepper. Add sliced sausage to the pot. Stir to combine all the ingredients.
Bring to a boil, cover, reduce heat and continue to simmer for up to 1 hour or until the barley is cooked. Serve with crusty Italian bread.