Place two large sheets of foil perpendicular to each other in an 8x11 baking dish (or similar size) to create a foil sling.(This makes removing the granola bars from the pan much easier.) Set aside.
In a large bowl, add the oats and crispy rice cereal. Stir to combine. Set aside.
In a medium microwave-safe bowl, add the peanut butter, honey, brown sugar and salt. Stir to combine. Heat (high/100% power) in microwave for 1 minute. Remove from the microwave and stir with a whisk. Place back in the microwave and heat (high/100% power) for 1 more minute. Remove from the microwave and add the vanilla. Stir with a whisk until smooth.
Pour the peanut butter mixture over the oats and crispy rice cereal. Stir to fully combine and the oat mixture is fully coated.
Pour the mixture into the prepared dish. Firmly press the mixture into the baking dish and make a smooth and even surface. (I use a pastry roller for this step.)
Cover with plastic wrap and place in the refrigerator for 30 minutes.
Using the foil sling, remove the mixture from the dish. Cut into rectangles.