While your grill preheats, whisk together olive oil, balsamic vinegar, garlic powder, salt, black pepper, dried oregano, fresh lemon zest, and chopped fresh herbs in a large bowl. This creates your flavor base. Meanwhile, prepare all vegetables: cut bell peppers into 1-inch wide strips, slice zucchini and yellow squash into 1/2-inch thick rounds, trim the ends from green beans, halve the cremini mushrooms, snap off the woody ends from asparagus spears, and cut red onion into thick wedges. I like to keep vegetables relatively uniform in thickness so they cook at similar rates on the grill.

Pour the marinade mixture over all prepared vegetables and toss gently until everything is evenly coated. Now separate your vegetables into three groups based on their cooking requirements: (1) quick-cooking delicate items—asparagus and green beans—which will go in a foil packet, (2) medium-cooking items—mushrooms and zucchini slices—which will go in a grill basket, and (3) sturdy vegetables—bell pepper strips, squash rounds, and red onion wedges—which will be grilled directly on the grates. This organization ensures each vegetable reaches perfect tenderness at the right time.

Heat your grill to medium-high heat. Once hot, place bell pepper strips, yellow squash rounds, and red onion wedges directly on the grill grates. Cook for about 2 minutes per side until you see nice grill marks and the vegetables begin to soften. These heartier vegetables need direct heat and will be ready in about 4 minutes total. Transfer them to a serving platter and keep warm.

Create a foil packet by tearing off a large sheet of heavy-duty foil. Place the asparagus spears and green beans in the center, drizzle with any remaining marinade from the bowl, then fold the foil to create a sealed packet. Place this on the grill grates at medium-high heat for 15-20 minutes. I prefer foil packets for delicate vegetables because they steam gently inside and won't fall apart through the grates. Around the 12-minute mark, carefully open the foil (watch out for steam!) to check for tenderness.

While the foil packet is cooking, place the halved cremini mushrooms and zucchini slices into a grill basket (this prevents smaller pieces from falling through). Set the basket on the grill grates at medium-high heat for 10-12 minutes, stirring every 3 minutes to ensure even cooking and prevent sticking. The mushrooms will release moisture and develop a nice golden color, while the zucchini becomes tender with light charring.

Once all vegetables are cooked through and tender, transfer them to a large serving platter. Arrange them in an appealing pattern, combining all the grilled vegetables together. Taste and adjust seasoning with additional salt and pepper if needed. Serve immediately while still warm, allowing guests to enjoy the charred edges and tender interiors of each vegetable.