Prepare chipotle marinade mix according to directions. Coat all watermelon slices on each side with marinade; discard any remaining marinade.
Coat grill surface with corn oil. Preheat grill to its highest setting or to 500°F. Grill each side for about 5 minutes or until there is a nice slightly brown color with noticeable grill marks.
Recipe courtesy of David Grotto, RD, LDN.