Marinated Vegetable Kebabs

In large bowl, combine broccoli, summer squash, red peppers, and onions; set aside. In small bowl, mix together oil, vinegar, soy sauce, red pepper flakes, ginger, and garlic salt. Add oil mixture to vegetables; marinate at room temperature 1 to 2 hours, tossing occasionally. Thread vegetables alternately onto long skewers. Place kebabs on grill grid over medium coals. Grill 5 to 7 minutes, turning occasionally; baste with marinade.