Preheat your oven to 350°F (175°C). Grease a 9x13-inch baking dish or line it with parchment paper.
In a large bowl, cream together butter and sugar until light and fluffy. Beat in eggs one at a time, then add vanilla.
In a separate bowl, whisk flour, baking powder, and salt. Gradually add dry mixture to wet ingredients, mixing just until combined.
Fold in red, white, and blue sprinkles with a spatula.
Press dough evenly into the prepared baking dish. Sprinkle extra sprinkles on top.
Bake for 20–22 minutes, or until edges are lightly golden and center is set.
Let cool completely in the pan. Slice into squares or use a star-shaped cookie cutter for added flair!