Preheat oven to 250º and line a large baking sheet with parchment paper. Cut each slice of cheese into 9 squares and place in a medium bowl. Add taco seasoning and toss to coat.
Lay cheese slices in an even layer (make sure none are overlapping!) on prepared baking sheet. Bake until crisp and golden, 40 minutes (they will crisp up even more when cooled). Let cool 10 minutes, then remove from parchment paper.