Pop popcorn according to package directions and remove all unpopped kernels. Place popped popcorn and granola in a large roasting pan. Place the pan in the oven to keep everything warm while you make the caramel.
Cook maple syrup and corn syrup in a medium saucepan over medium heat, stirring occasionally. Once the temperature reaches 230-235°F on a candy thermometer, allow the mixture to cook for an additional 3 minutes.
Immediately pour the mixture over the popcorn mixture. Stir well to evenly coat.
Bake mixture at 250°F for 1 hour, stirring every 15 minutes. Allow to cool completely, then tap the pan on the countertop to break into clusters.