Whisk dressing ingredients together until blended and set aside.
Toss shrimp with cumin, brown sugar and ¼ cup oil. Slide onto skewers. Grill over hot coals about 3–4 minutes on each side until done.
Brush lettuce with ¼ cup oil. Grill 1–2 minutes on each side just to get a light char. Remove to serving platter.
Brush corn and peppers with ¼ cup oil. Grill until corn is roasted and peppers are a bit charred. Remove and let cool. Cut corn from cob. Scatter toppings and shrimp about lettuce on platter.
Serve with dressing.