• 3 red onions , cut into 1/4-inch slices
• 3 yellow onions , cut into 1/4-inch slices
• 1/4 cup extra-virgin olive oil
• 3 tablespoons balsamic vinegar
• 1 teaspoon salt
• 1/2 teaspoon freshly ground pepper

Combine all ingredients and divide between 2 shallow pans. Allow to sit at room temperature 30 minutes to 1 hour.

Place the onion slices on grill (flame should be low) by using a vegetable tray or by laying directly on grill (be careful not to let them fall through; rings will break up). Turn once or twice until tender; grill about 20 to 30 minutes.