Instructions: Combine oil, vinegar, garlic, salt, and pepper; mix well. Brush over both sides of mushrooms and onion slices. Hold onion rings together by inserting a toothpick through each slice. Grill mushrooms and onions on covered grill over medium coals until tender, about 5 minutes per side. Place rolls cut side down on grill during last 1-2 minutes of cooking.

Remove toothpicks from onions. Layer lettuce, tomato and onion rings over bottoms of rolls; top with mushrooms. Close burgers with tops of rolls; serve with mustard, ketchup or fat free mayonnaise if desired.

Makes 4 burgers.

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