To Prepare Vegetables for Grilling:
Cut the zucchini and squash into 1/2 thick planks lengthwise. Cut the sides off of each pepper. Place the zucchini, squash, asparagus spears and pepper sides into a large bowl and toss with salt, pepper and a drizzle of olive oil. Cut the Baguette on the bias into 1/2 inch thick slices and brush with olive oil.
Grill the baguette slices over a burner set to medium heat turning when golden brown and grill marks have developed. Place the vegetables, a few pieces at a time, over the sear burner turning after a couple minutes to develop grill marks on both sides. Remove to a second large bowl or plate. After all vegetables have been grilled, cut vegetables into bit size pieces and toss of balsamic vinaigrette to taste. Transfer to a serving platter and sprinkle with crumbled feta.
Serve with toasted crostini.