Preheat the oven to 175°C.
Line a 20cm x 30cm slice tin with baking paper.
In a large bowl, whisk together the flour, oats, baking powder, baking soda and salt.
In another bowl, whisk the oil, brown sugar, white sugar, eggs, peanut butter and vanilla until smooth and well combined.
Add the dry ingredients to the wet with most of the chopped dark chocolate, and fold in until just combined.
Spread the mixture evenly into the prepared tin.
Press the remaining chocolate and the peanuts into the top.
Bake for 25 minutes, or until risen and just golden around the edges.
Cool in the tin before slicing into bars.
