Toss popcorn, cranberries, and pecans in large heatproof bowl; sprinkle with salt.
Melt butter in large microwave-safe bowl on high for about 40 seconds. Stir in marshmallows; microwave on high for 1 minute and 15 seconds, stopping once halfway through to stir. Stir until mixture is melted and smooth.
Pour marshmallow mixture over popcorn mixture, folding with rubber spatula until well-combined. Let cool enough to handle.
Oil hands; form mixture into 15 evenly-sized balls, pressing firmly.