Set oven control to broil. Line cookie sheet with foil. Place poblano chiles on cookie sheet. Broil 8 minutes, turning once, until blackened. Place blackened chiles in bowl; cover tightly. Let stand 10 minutes.
Meanwhile, place corn and onion on same cookie sheet. Broil 10 minutes, stirring after 5 minutes.
Bake 15 minutes or until peppers are tender and stuffing is hot.
Heat oven to 350°F. Cut each bell pepper in half; remove seeds and membranes (leave stem on, if desired). Fill pepper halves with quinoa mixture; sprinkle evenly with cheese. Place on cookie sheet.
Peel off charred skin from blackened chiles; coarsely chop chiles. Place in medium bowl. Add broiled corn and onion, oil, lime juice, oregano, cumin, salt and pepper. Add tomatoes and cooked quinoa; toss.