Preheat the grill* to medium-high heat. In a large mixing bowl toss together the sliced onion and zucchini with oil to coat lightly before grilling.
Place your whole peppers and the oiled onion and zucchini on the hot grill. Grill the vegetables, turning occasionally until tender and slightly charred, for roughly 5-10 minutes (flipping halfway through). The peppers will take a bit longer to grill as you want to really blister the skin to get that tender sweet roasted pepper on the inside.
Remove your veggies from the heat and allow to cool slightly before handling to remove seeds and burnt skin (some skin left on is fine). Slice the peppers into thick strips.
To make the salad dressing: In a small mason jar add in all of the ingredients, screw on the lid and shake well to combine.
Transfer the peppers, onion and zucchini to a large salad bowl with tomatoes and parsley. Toss with your dressing.
Enjoy warm or chill in the refrigerator for 1 hour. You can store the remaining salad in an airtight container in the fridge for up to 3 days.