1Combine drained tomatoes, cheese, avocado, green onions and garlic salt in medium bowl; blend well.
2Spread 1/3 cup refried beans over entire surface of 5 flour tortillas; top each with tostada shell. Spoon tomato mixture evenly over shells; top each with a remaining flour tortilla to make 5 quesadillas stacks.
3Spray large skillet with cooking spray; heat over medium heat until hot. Brown both sides of each quesadilla stack in skillet until golden brown. Cut each into 4 wedges to serve