Add chiles, onion and mushrooms; cook 10 minutes, stirring frequently, until vegetables are tender.
Divide vegetable mixture evenly onto 4 tortillas.
Sprinkle each with 3 tablespoons cheese.
Top with remaining tortillas.
Wipe skillet clean with paper towels.
Spray skillet with cooking spray; heat over medium heat.
Place 1 quesadilla in skillet; cook 1 to 2 minutes or until golden brown on bottom.
Turn; cook 1 to 2 minutes longer or until golden brown on bottom and cheese is melted.
Remove from skillet to serving platter; cover with foil to keep warm.
Repeat with remaining quesadillas.
Notes & Wine Advice
For a spicier flavor, spread each tortilla lightly with salsa. Then top with the vegetables and cheese. If you want to walk on the mild side, 1 green bell pepper can be substituted for the poblano chiles.