Preheat oven to 200°C (400°F). Line 13 x 9 in. (3 L) baking dish with aluminum foil.
In small bowl, whisk together maple syrup, oil, salt and pepper. In large bowl, toss whole onions with half the maple syrup mixture (reserve remaining half). Place onions in lined baking dish and also cover with foil. Bake 55 min., or until onions are tender and turning golden brown around edges. Remove foil cover. Brush with remaining maple mixture and continue baking for an additional 25 to 30 min. (replace foil cover if onions brown too quickly). Serve sprinkled with parsley.
To make a delicious onion soup, simply purée the roasted onions with 2 to 4 cups (500 mL to 1 L) vegetable stock, depending on desired texture. Heat to serve.