Heat large nonstick skillet coated with cooking spray on medium heat.
Place tortillas into the skillet one at a time and heat each side 1 minute. Set aside on plate.
Re-spray skillet with nonstick spray and return pan to heat. Add onions and mushrooms, and cook 5 minutes, or until onions are transparent. Add tomatoes and cook 2-3 minutes. Remove from heat and set aside.
Mix eggs in mixing bowl and pour into skillet. Let set 1 minute. Add cooked vegetables and cheese, and stir gently 2-3 minutes, or until all ingredients are scrambled.
Top tortillas with eggs and season with garlic, salt and pepper, and top with salsa or guacamole.