With the heat of your grill on medium (see note) cook the veggies. The husks of the corn should be removed so they can char slightly. The onions should be sliced and then placed on the grill with the rings of each slice still together.
Flip all the veggies after about five minutes. Cook everything but the red pepper for 10 minutes total, and keep the red pepper on there for about 15 minutes, flipping several times so each side gets well cooked.
Once the veggies have slightly cooled, cut the corn from the cob, dice the onions, peel the skin from the peppers and dice them. Add all the veggies to a large bowl.
In a blender combine the olive oil, vinegar, chipotle peppers, adobo sauce, salt, and garlic.
Combine the quinoa and the veggies together. Chill for at least 2 hours.
Before serving, pour about 2/3 of the dressing over the salad and add more spoonfuls as necessary to taste.