Pierce sweet potatoes several times with tines of a fork. Place on a microwave-safe plate; cover with damp paper towels. Microwave at HIGH 6 to 8 minutes or until tender. Let stand 5 minutes. Peel and cut in half lengthwise. Cut into (1/2- x 3-inch) strips. Coat evenly with vegetable cooking spray, and sprinkle evenly with salt.
Coat cold grill cooking grate with cooking spray, place on grill over medium-high heat (350° to 400°). Place potato strips on grate.
Grill potatoes, covered with grill lid, for 1 to 2 minutes on each side or until grill marks appear on fries.
Note: For testing purposes only, we used an 1,100-watt microwave oven.