1. Slice 2 small zucchini and 2 small yellow squash 3/4 inch thick. Thread 2 pounds boneless, skinless chicken thighs, cut into pieces, on 8 metal skewers, alternating with zucchini and squash.
2. Whisk together 1/3 cup spicy-brown mustard, 3 tablespoons dark-brown sugar, 3 tablespoons olive oil and 1 teaspoon garlic powder in small bowl. Brush over skewers.
3. Grill or broil for 10 to 12 minutes, turning halfway through cooking, until chicken is cooked through. Serve over rice. Makes 8 servings.