Pre-heat a lightly oiled grill (or grill pan) over medium-high heat. (If you have a grill basket, you may want to use it for the asparagus and onion.)
In a small bowl combine the olive oil and garlic.
Pat the zucchini and squash dry with a cloth or paper towel to remove any excess moisture. Brush the vegetables all over with the olive oil mixture and season them with kosher salt and black pepper.
Place the vegetables on the hot grill and let them cook until they’re tender (but not mushy!) and have developed grill marks. The vegetables will have slightly different cooking times: roughly 5 minutes for the asparagus (turn them every 1 to 2 minutes); 7 to 8 minutes for the zucchini and squash (3 to 4 minutes per side); and 8 to 10 minutes for the bell pepper and onion (4 to 5 minutes per side).
Meanwhile warm the Tomato Basil Sauce in a medium saucepan until simmering. You can do this on a cooler section of the grill or on the stovetop over medium-low heat.
Add the Tomato Basil sauce to the base of a large shallow serving bowl or platter. Arrange the grilled vegetables on top of the tomato sauce. Top with basil, parsley and crumbled feta. Serve warm