Line an 8 x 8-inch pan with parchment paper and set it aside.
In a large bowl, combine the rolled oats and protein powder until evenly mixed.
Place the peanut butter and honey (or brown rice syrup) in a microwave-safe bowl and heat in 20-second intervals, stirring between intervals, until the peanut butter softens and the mixture is smooth and thick.
Pour the warm peanut butter mixture into the dry ingredients and stir until fully combined. If using chocolate chips, fold them in at the end.
Transfer the mixture to the prepared pan and press it firmly and evenly into the pan so the surface is smooth.
Refrigerate for at least 1 hour to firm up, then lift the mixture from the pan using the parchment and slice into 20 bars.