In a large bowl, lightly coat the zucchini, yellow squash, bell peppers and eggplant with extra virgin olive oil.
Lightly season vegetables with salt and pepper. Brush olive oil on corn and season with salt and pepper.
Heat grill to medium-high heat. Using a paper towel, lightly coat the grill with some olive oil to help prevent sticking during cooking.
Add the vegetables to the grill. Cook the zucchini, yellow squash, bell peppers and eggplant for 3 minutes on each side with the grill closed, 6 minutes total.
The vegetables should be tender yet hold its shape. Cook the corn turning every few minutes so all sides get cooked on the grill and kernels are tender, 12 to 15 minutes.
Refrigerate the grilled vegetables until chilled.
Cut the kernels off the cob and transfer to a large bowl. Cut the zucchini, yellow squash, bell peppers, and eggplant into ½-inch pieces and add to the bowl. Add cut tomatoes, sliced shallots, and spinach to the bowl. Toss gently until just mixed. Refrigerate until ready to use.
Citrus Vinaigrette
In a medium-sized bowl, whisk together the apple cider vinegar, lemon and lime juices, and honey.
Gradually whisk in the olive oil, continuously whisking until a thickened vinaigrette is achieved (no large oil droplets seen).
Add the minced shallots, parsley, salt, and pepper, adjusting seasoning as needed.
Serve salad with the dressing on the side or toss with the vinaigrette.