Preheat your oven to 300 degrees. Put the popped popcorn, removing in unpopped kernels, into a large bowl.
In a small saucepan over medium low heat, melt the butter, sugar, corn syrup & red hot candies. This will take a bit of time for the candies to completely melt. Stir occasionally as it heats.
Once everything is completely melted, slowly pour the sauce over the popcorn, tossing to evenly coat.
Spread the popcorn out onto 2 large baking sheets. Bake for 20 - 30 minutes, stirring every 10 minutes. Remove from the oven and let cool before serving.