Prep vegetables as indicated. Assemble peppers, cherry tomatoes, and garlic cloves on separate skewers. (If using a grill pan, make sure the vegetables are not crowded and will cook evenly.)
Arrange sliced squash, onion discs, and skewers on a rimmed baking sheet and brush with olive oil to lightly coat. Season generously with salt and pepper, then sprinkle with herbs.
Grill over med-high heat until browned with grill marks on each side until crisp-tender, 6-8 minutes. Brush with olive oil on uncooked side just before turning. Remove each type of vegetable when done and place back on the rimmed baking sheet.
Remove skewers from tomatoes, peppers, and garlic. Squeeze the ends of the garlic to remove peel (roasted garlic should pop right out) and slice squash into bite-size pieces.
Keep in a warm oven until ready to serve. Mix vegetables together on a large serving tray, taste and season with salt and pepper, as needed; serve warm.
Suggestions for leftovers:
Use leftovers for frittatas, soups, Alfredo, pizza, rice pilaf, fajitas, and salads.
Grilled vegetables can be frozen, however there is a change in texture. Once frozen, use in recipes like soups, casseroles, or a frittata where the texture is not as pronounced.