Adjust the oven rack to the middle position. Preheat the oven to 425 degrees.
Brush a rimmed baking sheet with oil.
Spread the four tortillas out on each corner of the pan.
In a bowl, combine the mozzarella cheese, Monterey Jack cheese, black beans, and taco seasoning in a bowl.
Fill each tortilla with the cheese and bean mixture, about one cup per tortilla. Leave a 1-inch border around the edges, so the cheese doesn’t spill out once it melts.
Close the tortillas and use a spatula to press firmly.
Top with a second baking sheet on top of the quesadillas. (This helps them get crispy on both sides.)
Bake for 10-12 minutes until the tortillas are golden brown on both sides.
Let cool for 5 minutes, then slice the quesadillas into wedges and serve.
