A bar cookie is a cookie baked as a single slab in a baking pan and cut into rectangles or squares afterward, rather than baked as individual drop cookies or rolled cookies.
The dough or batter is pressed or poured into the pan and baked until set, then cooled and cut into pieces once solid. This makes bar cookies quick to produce in quantity, and the pan format easily accommodates layers or swirls of nuts, dried fruits, chocolate chips, or caramel.
Common examples include brownies, lemon bars, date bars, and oatmeal bars, ranging in texture from soft and fudgy to crisp and crumbly. Some bar-cookie pans have individual compartments to produce uniform pieces, particularly for layered or filled recipes.