Heat a grill or grill pan over high heat until hot, add the corn and char on all sides, turning occasionally, for 8-10 minutes. Remove from grill and set aside. When corn is cool enough to handle, cut the kernels off the cobs. Set aside.
Place the potato quarters in a large pot and cover with water. Cover pot and bring to a boil over high heat, then reduce to medium-low and simmer for 15 minutes, or until potatoes are fork tender. Drain water and allow potatoes to cool slightly before removing the skins and cutting into bite sized cubes. Set aside.
In a large bowl, mix together the mayonnaise, sour cream, cotija cheese, onion, garlic powder, chili powder, and lime zest. Add the potato cubes and the reserved charred corn kernels and mix well. Add additional salt to taste, if necessary.
Top with extra cotija cheese and/or chopped cilantro, if desired. Serve with lime wedges at room temperature or cover and store in the refrigerator until ready to use.
Store potato salad covered in the refrigerator for up to 5 days.
If you can't find cotija cheese in local grocery stories, just substitute feta cheese.
Can substitute frozen corn kernels for fresh corn, just be sure to thaw the kernels first prior to adding to the potato salad. Trader Joe's has frozen charred corn kernels that I've used in this recipe when my stores didn't have fresh corn on the cob.