Pierce the fresh bratwurst skins in several places with a fork or with the tip of a sharp knife.
In a covered grill, arrange preheated coals around a drip pan. Test for medium** heat above the pan. Place the bratwurst on the grill rack over the drip pan. Cover and grill for 10 minutes. Turn bratwurst. Grill, covered, for 10 to 15 minutes more or until sausage juices run clear and skins are golden.
Meanwhile, place rolls, cut sides down, on grill rack over coals for 1 to 2 minutes or just until toasted. Spread with butter or margarine. Arrange 2 bratwurst on bottom halves of each roll. Add pickles, mustard, catsup, and onions (or pass the condiments). Place tops of rolls on filling. Makes 4 servings.
To test for medium heat, you should be able to hold your hand over the coals at the height of the food for 4 seconds before you have to pull away.
Trim the fat and sodium by serving just one bratwurst per bun, instead of two.