Peel and cut sweet potatoes into 1” cubes. Toss sweet potatoes and red onion with olive oil, salt, and pepper, and place on a parchment lined baking sheet. Use 2 baking sheets if necessary to avoid overcrowding.
Bake sweet potatoes for 35-40 minutes, tossing every 15 minutes to allow all sides to brown evenly. Remove and allow to cool.
In a large bowl, whisk together the French Dressing and red wine vinegar. When potatoes have cooled, toss in the dressing to coat. Top with fresh parsley and serve at room temperature.