1 medium yellow squash, sliced on bias
1 medium zucchini, sliced on bias
1 medium eggplant, sliced into 1/2-inch thick circles
1 red onion, sliced in 1/2-inch thick circles
1 red bell pepper, stemmed, seeded, and quartered
1 yellow bell pepper, stemmed, seeded, and quartered
2 portobello mushroom caps, gilled and peeled
1 bunch green onions
Freshly ground black pepper
1/2 cup extra-virgin olive oil
1/2 cup golden balsamic vinegar
Preheat grill to high.
Prepare all vegetables. Place vegetables in a roasting pan with the mushroom caps and green onions. Season vegetables generously with salt and pepper, and toss with the olive oil and balsamic vinegar. Place vegetables, cut side down, on the hot grill and cook for a couple minutes on each side, or until tender and nicely marked by the grill.
Remove from grill and toss with an additional 1/4 cup balsamic vinegar. Season with salt and pepper, to taste.