Slice the tomatoes in half and place in serving bowl. Sprinkle with salt and set aside for at least 20 minutes to allow the salt to extract some of the juices.
Cut the squash, onion and mushrooms into bite size pieces, and toss with a little olive oil, salt and pepper, and place on a grill pan. Slice the bread in half and brush lightly with olive oil.
Grill the vegetables on a medium-high flame until squash is tender. This could take about 20 minutes. Stir the veggies around every couple of minutes to grill evenly.
Toast the bread on the grill for about 30 seconds on each side, or until lightly browned.
Cube the bread and add to the tomatoes in the bowl. Stir in the grilled vegetables. Drizzle with Olive Oil and Red Wine Vinegar. Add chopped thyme and parsley, a pinch of garlic powder, and salt and pepper to taste.
Let sit for 20 minutes or more before serving. Serve at room temperature.