Line a 9-inch square baking pan with foil, allowing ends to overhang by 2 inches.
Process graham crackers with sugar and salt in a food processor until finely ground. Pulse in butter until moistened. Transfer to lined pan and press crumbs down evenly and firmly.
Place butterscotch morsels in a large bowl and microwave on high for 1 minute. Remove and stir until smooth and creamy. (Continue to microwave in 10-second intervals if morsels have not melted. Do not overheat or mixture will seize up and turn into a stiff mass.) Stir in peanut butter and peanuts. Blend well and spread evenly over graham-cracker crust. Cover and chill for at least 1 hour 30 minutes or until firm.
Lift bars out and remove foil. Use a sharp knife to carefully cut into squares.