Not only do these veggies look and taste great, but they cook quickly, there’s no mess, you can serve them at any temperature, and you can make them ahead of time. Plus, the leftovers can be used on sandwiches or in salads, as condiments or side dishes.
Prepare a Charcoal or gas grill for medium-high heat, or preheat a ridged grill pan over a medium-high flame. Brush the vegetables with ¼ cup of the oil to coat lightly. Sprinkle the vegetables with 1 teaspoon each of salt and pepper. Working in batches, grill the vegetables until tender and lightly charred all over, about 12 minutes for the bell peppers; 7 minutes for the yellow squash, zucchini, eggplant, and mushrooms; and 4 minutes for the asparagus and green onions. Arrange the vegetables on a platter.
In a small bowl, whisk the vinegar, garlic, parsley, basil, rosemary, the remaining 2 tablespoons of oil, and ½ teaspoon each of salt and pepper to blend. Season with more salt and pepper to taste. Drizzle the dressing over the vegetables, and serve warm or at room temperature.