Preheat oven to 350 degrees F. Line a 9x9 baking pan with parchment paper. Alternatively, if you don't have parchment paper, grease the pan instead. 

In a large bowl, mix together the oil, sugar and vanilla. Add in the eggs, one at a time until well combined. Set aside while you work on the dry ingredients. 

In a separate bowl, combine the flour, cocoa, baking powder and salt. 

Now add the dry ingredients into the wet ingredients slowly, about 1/2 cup at a time until everything is well combined. 

Pour the batter into the prepared pan and spread evenly. 

Bake for 25-30 minutes. Check for doneness by inserting a toothpick into the center of the brownies. Brownies are done when the toothpick comes out clean. If the toothpick comes out wet, cook brownies for 5 more minutes and then check again. 

Allow brownies to cool for at least 10 minutes on a wire rack in the pan before removing and cutting.