Preheat your oven to 350°F (175°C).

Grease a 10.5 x 15.5-inch jelly roll pan with butter or cooking spray.

In a large mixing bowl, combine oil, granulated sugar, brown sugar, eggs, and vanilla extract. Whisk until smooth and creamy, about 2-3 minutes.

In another bowl, sift together flour, rolled oats, baking powder, salt, and cinnamon. Stir gently until well combined.

Fold the shredded zucchini into the batter using a rubber spatula.

Spread the zucchini batter evenly in the prepared pan and bake for about 18-22 minutes. Check doneness with a toothpick.

Once baked, let the bars cool completely in the pan on a wire rack, about 30-45 minutes.

In a medium bowl, beat together softened cream cheese and butter until smooth, then gradually add powdered sugar.

Once cooled, spread the frosting generously over the bars, slice them into squares, and serve.