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.
- Place onions on grid over medium, ash-covered coals. Grill 15 to 20 minutes or until tender, turning occasionally and brushing with oil. (Grilling times for onions remain the same on gas grill.) Grill patties in center of grid, covered, 8 to 10 minutes (over medium-heat on preheated gas grill 7 to 9 minutes) until instant-read thermometer inserted horizontally into center registers 160°F, turning occasionally. Season burgers with salt and pepper, as desired.
Place 1 burger on bottom of each bun; top evenly with cheese and grilled onions. Close sandwiches.
Nutrition information per serving: 431 Calories; 183.6 kcal Calories from fat; 20.4 g Total Fat; 8.2 g Saturated Fat; 0.2 g Trans Fat; 3.4 g Polyunsaturated Fat; 6.3 g Monounsaturated Fat; 105 mg Cholesterol; 430 mg Sodium; 27 g Total Carbohydrate; 0.7 g Dietary Fiber; 4.9 g Total Sugars; 35 g Protein; 0 g Added Sugars; 238 mg Calcium; 4.6 mg Iron; 504 mg Potassium; 0.1 mcg Vitamin D; 0.4 mg Riboflavin; 8.1 mg NE Niacin; 0.5 mg Vitamin B6; 3.1 mcg Vitamin B12; 375 mg Phosphorus; 7.6 mg Zinc; 39.3 mcg Selenium; 106.4 mg Choline;