Classic restaurant favorite, customizable with your choice of cheese.
1. Combine Ground Beef, thyme and garlic in medium bowl, mixing lightly but thoroughly. Lightly shape into four 1/2-inch thick patties. Brush both sides of onion slices with oil.
2. Place patties in center of grid over medium, ash-covered coals; arrange onion slices around patties. Grill, covered, 8 to 10 (over medium heat on preheated gas grill, 7 to 9 minutes) until instant-read thermometer inserted horizontally into center registers 160°F, turning occasionally. Grill onions 15 to 20 minutes or until tender, turning occasionally and brushing with oil. (Grilling times for onions remain the same on gas grill.) Season burgers with salt and pepper, as desired.
3. Place 1 burger on bottom of each bun; top evenly with cheese and grilled onions. Close sandwiches.
Test Kitchen Tips Cooking times are for fresh or thoroughly thawed Ground Beef. Color is not a reliable indicatior of Ground Beef doneness.