Add 2 cups water, the barley, lentils, and ¼ teaspoon salt to a 12-inch skillet and bring to a simmer over medium heat. Reduce the heat to low, cover, and cook for 20 to 25 minutes or until tender, but still chewy.
While the grains cook, combine the cranberries, walnuts, lemon juice, olive oil, parsley, and ½ teaspoon remaining salt in a medium bowl. Season with pepper.
When finished cooking, drain the barley-lentil mixture and add the hot grains to the cranberry mixture in the bowl. Toss to mix. Taste for seasoning and more lemon, salt, or pepper if needed. Serve warm.
