Pull back husks on corn, remove silk, and fold husks back over corn. Soak corn in large pot of cold water for 30 minutes.
Preheat your grill (medium-high heat). Drain the corn. Grill the corn until the kernels are just tender, turning occasionally, about 8 minutes. Pull back the husks. Spread the corn with mayonnaise; sprinkle with cheese, chili powder, salt and pepper. Arrange the corn on a platter. Serve with lime wedges.
Queso fresco can be found in the specialty cheese section of most markets (and in Latin markets). Feta may be substituted.
If counting WW Points, use light mayo for this recipe.