Mix first 4 ingredients in large bowl. Season with pepper. Divide mixture into quarters. Shape each into 3/4-inch-thick patty. Mix tomatoes and mayonnaise in small bowl to blend.
Prepare barbecue (medium-high heat).
Grill burgers, onions and peppers until burgers are cooked through and onions and peppers are lightly charred, turning occasionally, about 10 minutes.
Move peppers and onions to cool side of grill. Top burgers with cheese. Place rolls on grill cut side down. Cover with lid and cook until cheese melts and buns are heated through, about 2 minutes.
Servings: