Start by grilling the vegetables. Turn on your grill to medium heat.
Remove the stems from the mushrooms and place on a plate or baking sheet. Cut the ends off the onion and slice it into 1/4" thick slices. Add to the plate.
Cut the ends off the squash and zucchini and cut those into 1" rounds. Place those on the baking sheet.
Trim the ends off the asparagus and add that to the baking sheet as well.
Drizzle all the vegetables with the olive oil and sprinkle with salt and pepper.
Place the veggies directly on the grill and cook for 3 - 4 minutes, before flipping. Remove the aspargus when you flip the other veggies. Cook all the other veggies for another 2 - 3 minutes.
Remove from the grill and allow to cool while you prep everything else.
Whisk together all the ingredients until smooth and creamy. If dressing is too thick, add a splash or two of water.
When ready to serve, cut the veggies into bite size pieces. Add the greens into a large salad bowl and top with grilled veggies. Crumble up some feta and cube the avocado. Drizzle with dressing and enjoy!