Position an oven rack in the center of your oven and heat the oven to 300F degrees. Line a 13 by 9-inch baking pan with aluminum foil and coat the foil lightly with nonstick cooking spray.
Place the peanuts in a 12-inch skillet over medium heat, and toast, stirring often, until fragrant and golden brown, 3 to 5 minutes. Transfer to a large bowl. Add the oats and oil to the skillet and cook, stirring often, until golden and fragrant, about 5 minutes. Transfer the toasted oats to the bowl with the peanuts and stir in the salt.
Add the honey and brown sugar to the skillet and simmer gently over medium-low heat, stirring often, until the sugar is fully dissolved, about 5 minutes.
Remove skillet from the heat, stir in the vanilla, cinnamon, and peanut butter until well blended.
Working quickly, stir the hot honey mixture into the peanut-oat mixture until thoroughly combined. Transfer the mixture to the prepared baking pan and pack very firmly into an even layer. (I used the bottom of a measuring cup to pack the mixture down.)
Bake until the granola bars are golden, 20 to 25 minutes, rotating the pan halfway through baking.
Remove from the oven and allow the bars to cool in the pan for 10 minutes, then remove the whole slab from the pan using the foil.
Cut into 16 bars. Place the bars on a wire rack to cool completely.