Drain the brine from the jar into a large bowl.
Remove the pickles and lay onto a few sheets of paper towels. Dab with the paper towels to dry as well as you can.
Transfer the pickles to another large bowl.
Add the onion and drizzle with the oil. Toss gently to coat.
Fire up your grill.
Place pickles and onions onto the grill and grill on all sides until you get grill marks.
Remove and let cool slightly before returning pickles to the jar.
Add the onions and the reserved brine.
Seal and refrigerate until ready to use within 5 days.