The summer months bring plentiful amounts of zucchini and summer squash, among other vegetables. Look for squash with a vibrant, relatively even color and a firm stock. Avoid rubbery squash; it's older and has lost some nutritional value. Marinate your zucchini and summer squash before grilling or add a topping afterward, depending on your preference. Thicker sauces work especially well after grilling to avoid a mess.
Turn on or light your grill and prepare it for indirect-heat cooking. Turn gas grills on high and wait for charcoal to settle at medium-high temperature.
Place your vegetables next to the cutting board, along with a large, clean bowl. Slice a thin piece lengthwise from each individual zucchini and summer squash stock. This allows you set the vegetable on the cutting board and cut it without the bottom rolling around.
Chop the ends off each stock and toss them out. Slice each stock lengthwise, then slice it lengthwise again for spears. Slice the stock into discs if you prefer smaller pieces.
Marinate the zucchini and squash, if desired. Olive oil, seasoning and juices like citrus work well. Marinate for about 20 minutes.
Brush oil onto the grilling rack to prevent sticking. Place small squash chunks into a grilling basket or place spears directly onto the grill rack, directly over the hottest coals. Shut the grill lid only if you're using a gas grill. Lightly spray any tall flames with a water bottle if you're using a charcoal grill.
Grill the vegetables for three to four minutes on each side. They should have grill marks when ready.
Remove the squash from the grill and let it rest on a clean plate for several minutes before serving. Serve alone as an appetizer or as a side dish with your main meal.