1. Preheat grill for direct cooking over high heat (400°F). Brush pepper with ½ tsp. oil. Grill, uncovered, for 6 to 8 minutes or until tender and charred, turning occasionally. Transfer to a glass bowl; cover tightly and let stand 10 minutes. 
2. Peel and discard skin from pepper. Chop to make ⅓ cup. In a bowl, gently combine meat, roasted pepper, cheese, garlic, mustard, Worcestershire sauce, and black pepper. Form into 4 patties, about ¾ inch thick. Use your thumb to slightly indent the center of each patty, which prevents the middle from puffing while cooking. 
3. Adjust grill for direct cooking over medium heat (350°F). Brush onions with remaining ½ tsp. oil. Grill patties and onions, covered, for 6 to 8 minutes, until burgers are medium doneness (160°F) and onions are tender, turning burgers once and onions occasionally. 
4. Serve burgers with grilled onions in toasted buns with additional toppers and condiments. 
5. *Note: Chile peppers contain volatile oils that can burn your skin and eyes. When working with poblanos, wear protective gloves. 

Each burger contains: 541 calories, 19 g fat, 5 g saturated fat, 0 g trans fat, 94 mg cholesterol, 481 mg sodium, 52 g carbohydrates, 2 g fiber, 8 g sugar, 42 g protein. ","Daily values: 3% vitamin A, 50% vitamin C, 3% calcium, 27% iron.