Preheat oven to 425-degrees. Cut potatoes into 1-inch pieces. In a large bowl, whisk together mustard, olive oil, garlic and Italian seasoning. Add potatoes and toss to coat. Season with salt and pepper, to taste.
Grease an 8 ½" x 11" baking dish with olive oil and pour potatoes into the dish. Bake for 45 minutes, or until fork tender, stirring occasionally.
Use a pastry brush to evenly grease the baking dish with olive oil.