Lightly spray a cookie sheet with baking spray. Set aside.
Coat the corn on all sides with the oil and sprinkle with 1/4 teaspoon salt and pepper.
Place on the cookie sheet and roast in the oven for 20 minutes.
While the corn roasts, cook the bacon in a skillet until crisp. Remove from the skillet, reserving the drippings in the pan.
Add the sliced onions to the skillet and cook over low heat 15-20 minutes until the onions are soft and light brown. Sprinkle with a pinch of salt and pepper.
Allow the roasted corn to cool enough to handle before proceeding.
When the corn is cool enough to handle, stand it on its end in a large bowl and use a knife to cut the kernels off. Repeat with the remaining ears.
Add the bacon, onions, vinegar, parsley and remaining salt and pepper to the bowl. Taste and adjust the seasonings as needed. Serve warm. You can also chill this a day or two ahead and rewarm when you need it.