Spread beans evenly over 2 tortillas. Sprinkle evenly with 3/4 cup cheese, and drizzle with 1/4 cup taco sauce. Top with remaining tortillas.
Microwave 1 quesadilla, covered with a paper towel, on a microwave-safe plate at HIGH 1 to 1 1/2 minutes. Repeat procedure with remaining quesadilla.
Cut each into 8 wedges; serve with remaining 1/4 cup taco sauce, sour cream, and remaining 1/2 cup cheese.