Grilled Chicken Sausage & Veggie Packets Recipe

1 package (12 ounces) smoked chicken & apple sausage, cut crosswise into ½-inch pieces 6 medium red potatoes, cut into 1-inch cubes (about 1 pound) 2 medium ears fresh corn, silks and husks removed, cut crosswise into 2-inch pieces 1 medium red bell pepper, cut into 1-inch pieces 1 medium zucchini, cut into 1-inch cubes 1/2 medium red onion, cut into 1-inch wedges 2 tablespoons SE Grocers coarse ground Dijon mustard plus additional for serving (optional) 1 tablespoon chopped fresh parsley 1 tablespoon SE Grocers olive oil 1/4 teaspoon ground black pepper 4 (12-inch square) sheets SE Grocers aluminum foil