Assemble the ingredients together.
To make the dressing, combine all of the ingredients in a small bowl and whisk ingredients together. The dressing can be made ahead of time and stored for 3-5 days.
To grill the avocados, heat a grill pan or outdoor grill on high heat. Brush the olive oil on the flat side of the avocado halves.
Place the avocado halves, flat side down, on the grill. Grill for about 1-2 minutes or until grill marks are visible.
While the avocado is grilling, also place the ears of corn on the grill. Rotate so that each side gets slightly browned and cooked.
Carefully remove the avocado from the grill and season with salt and pepper. Slice the avocado into thin pieces with the grill marks visible. Set them aside on the cutting board for now.
Remove the corn from the grill and let it cool for a few minutes. Once the corn is cool enough to handle, use a knife to remove the kernels from the corn cob.
To make the salad, combine the quinoa, onion, cilantro, tomatoes, black beans and grilled corn kernels.
Pour a small amount of the dressing into the bowl. Gently toss so that all of the ingredients are coated with the dressing.
Divide the quinoa mixture onto four separate bowls or plates. Place one halved and sliced avocado on top of each serving.
Drizzle more dressing over the entire salad and serve immediately.
Garnish with lime wedges and cotija cheese, if desired.