In a small bowl, whisk together olive oil, garlic, Italian seasoning and onion powder; season with salt and pepper, to taste. Cut four sheets of foil, about 12-inches long. Divide broccolini and potatoes into 4 equal portions and add to the center of each foil in a single layer. Fold up all 4 sides of each foil packet. Spoon the garlic mixture over the broccolini and potatoes.
Fold the sides of the foil over the vegetables, covering completely and sealing the packets closed. Place foil packets in a single layer on a baking sheet. Place into oven and bake until tender, about 15-25 minutes.
Serve immediately, sprinkled with Parmesan and parsley, if desired.
