In 10-inch nonstick skillet, heat oil, garlic, cumin and salt over medium-high heat. Add mushrooms and bell pepper and onion stir-fry; cook 4 to 6 minutes, stirring frequently, until vegetables are crisp-tender. Sprinkle with cilantro and lime juice.
Spoon about 1/2 cup mushroom mixture onto each tortilla; roll up. Serve with guacamole and salsa if desired.