Portobello mushrooms, stem removed
Asparagus, trimmed of woody ends
Zucchini, sliced lengthwise
Scallions, trimmed of wilted parts
Red onions, cut into quarters, root attached
Sweet potatoes, cut lengthwise
Drizzle with olive oil, salt, and pepper; toss well to coat.
Heat grill to medium high. Place vegetables directly on grates and cook 4 to 5 minutes per side (depending on the vegetable – potatoes will take longer).