Remove portobello stems and brush mushrooms lavishly with marinade, set on a plate.
Peel and slice the onion into ½ inch thick rounds. Place on the plate with the mushrooms.
Shuck the corn, also place on the plate.
Slice the tomatoes in half. Slice the Avocado, chop the cilantro.Set aside.
Whisk the dressing ingredients together in a very small bowl.
Place the Portbellos ( gills up) sliced onion and corn on the grill. Turn heat to med-high. Baste onions with marinade. Cover and let all cook 5 minutes. Rotate mushrooms, flip onions ( baste) and turn corn. Cover. Let cook 3 minutes. Flip mushrooms, basting them, rotate corn, and remove any onions that are done, or move them to the side. Cook 2-3 more minutes. Remove.
On a large platter, lay down a bed of arugula or greens of your choice. Scatter with grilled onions. Slice the mushrooms and lay them over the top the onions. ( You could place them in two long rows if you want.) Place the tomatoes over the mushrooms, also in two long rows. Slice the corn off the cobb, and place over the tomatoes. Add avocado slices, chopped cilantro. Spoon the dressing over the entire salad. Sprinkle with a little salt and pepper and serve.
Add crumbled cheese if you like ( like goat, feta, queso fresco) or keep it vegan.