Spray 2 large, rimmed baking sheets with nonstick cooking spray.
Heat the oil in a large, heavy pot over medium-high heat until it is hot but not smoking. Add the popcorn kernels and cover the pot. Using pot holders, shake the pot constantly over the heat as the kernels pop, about 5 minutes, or until the kernels stop popping. Immediately spread the popcorn out on the prepared baking sheets.