In a small bowl, mix butter, cilantro, lime juice and lime zest. Shape into a log; wrap in waxed paper. Refrigerate until firm, about 30 minutes. Wrap each ear of corn in a piece of heavy-duty foil (about 14 in. square).
Grill corn, covered, over medium heat until tender, turning occasionally, 15-20 minutes. Meanwhile, cut lime butter into 12 slices. Remove corn from grill. Carefully open foil, allowing steam to escape. Serve corn with butter and, if desired, cheese.
1 ear of corn with 2 teaspoons butter (calculated without cheese): 145 calories, 9g fat (5g saturated fat), 20mg cholesterol, 67mg sodium, 17g carbohydrate (3g sugars, 2g fiber), 3g protein.