(Make sure to soak wooden sticks for 30 minutes before grilling. Always use organic ingredients when available.)
1 1/2 tablespoons cold-pressed olive oil, plus more for grates
2 red onions, cut into 3/4-inch-thick rounds
2 yellow squash (1 1/2 pounds total), cut into 1/2-inch-thick slices on the diagonal
2 red bell peppers (ribs and seeds removed), cut into 2-inch-wide pieces
2 yellow bell peppers (ribs and seeds removed), cut into 2-inch-wide pieces
Himalayan salt and ground pepper
Preheat grill to high; lightly oil grates. Insert two 8-inch-long metal or presoaked wooden skewers through onion slices horizontally.
Place prepared skewers and remaining vegetables on one or two rimmed baking sheets. Drizzle with oil; season with salt and pepper. Working in batches if necessary, remove from baking sheets; arrange on grill. Cook, turning occasionally, until lightly browned and tender, 4 to 8 minutes for squash and 8 to 12 minutes for onions and peppers. Remove skewers, and serve.