Preheat your oven to 350°F (175°C).
In a large mixing bowl, combine the vegetable oil, granulated sugar, light brown sugar, eggs, and vanilla extract. Whisk until well blended.
In another bowl, sift together the all-purpose flour, quick oats, baking powder, salt, and ground cinnamon.
Gradually add the dry mixture to the wet ingredients while stirring gently.
Gently fold in the grated zucchini using a spatula until just incorporated.
Pour the batter into a greased baking dish and spread it evenly. Bake for about 18 minutes or until a toothpick comes out clean.
While the bars are cooling, beat together cream cheese and butter until smooth. Gradually add confectioners' sugar and vanilla flavoring until well combined.
Once cooled, frost your Simple Zucchini Bars generously with the cream cheese frosting. Cut into squares or rectangles.