Wash the squash, cut out the stem and trim the bottom of the squash as well. Make thin horizontal slices through the width of the squash. I made ours about 1/2" to 3/4" thick and they grilled beautifully.
Brush both sides of the slices with olive oil. Sprinkle liberally with salt and pepper. Grill approximately 8-10 minutes, or until tender. Turn once as the squash is cooking.