Drain a 24-ounce jar of pickle halves, reserving the brine. Pat the pickles dry; toss with 1 onion (cut into wedges) and some olive oil. Grill, turning, until marked, 3 to 4 minutes. Let cool, then pack into a jar and add the brine. Refrigerate until cold or up to 5 days.
Photograph by Con Poulos