Preheat oven to 425 degrees F.

In a large skillet over medium-high heat, heat the oil. Add the duck legs and cook until golden brown on both sides, about 5 minutes per side.

In a medium bowl, combine the garlic, thyme, and salt. Rub the mixture onto the duck legs.

Put the potatoes in a roasting pan and place the duck legs on top. Roast in the preheated oven for 25 minutes, or until the potatoes are tender and the duck legs are cooked through.

Meanwhile, for the glaze, combine the oranges, sugar, and mustard in a medium saucepan over medium heat. Cook until the mixture is thick and syrupy, about 10 minutes.

Add the green beans and celery to the roasting pan and cook until the vegetables are tender, about 10 minutes.

Stir in the orange glaze and sprinkle with the parsley. Serve immediately.