Directly from the Better Homes & Gardens Test Kitchen experts, these strategies for preventing cookies and bars from adhering to the baking tray or pan will rescue your baking endeavors.
A freshly made, warm batch of homemade cookies or cookie bars is an ideal treat to delight family and friends. However, it's frustrating when you invest time and resources into making sugar cookies or whoopie pies, only to have them merge into a single giant cookie or, even worse, stick to the baking tray or pan.

How to Prevent Cookies from Sticking to the Baking Sheet
Thanks to the expertise of the Better Homes & Gardens Test Kitchen, we've accumulated some straightforward tips to ensure your cookies (or other baked goods) don't stick. We'll guide you on whether to bake your cookies on a greased or ungreased sheet and share how to cool them properly, so they remain intact.
1. Follow the Recipe Precisely

• Cookie and bar recipes are generally more forgiving than cakes, but all baking relies on chemistry. Making substitutions not specified in the recipe or using incorrect amounts of ingredients can cause cookies to spread too much or become hard and crumbly. Here are some common issues that could lead to less-than-ideal cookies if the recipe isn't followed exactly:
• Bars and cookies can become too tender to remove if you use too little flour or too much sugar.
• Use the exact type of fat (butter, oil, or shortening) called for in the recipe. Don't substitute shortening for butter or butter for shortening. It changes the consistency of the cookie or bar and yields unpredictable results.
• You can substitute high-fat (at least 100 calories per tablespoon) stick margarine for butter, but never use low-fat margarine, as it can make cookies and bars flat and harder to remove from the pan.
• Unless specified, use large eggs for baking, so your cookies and bars maintain their structure.

Andy Lyons

2. Grease Your Baking Sheet or Pan
Some recipes suggest using ungreased pans or cookie sheets because there's enough fat in the crust or batter to prevent the cookies or bars from sticking. If you grease the cookie sheet when the recipe calls for an ungreased sheet, your cookies might spread excessively (looking at you, chocolate chip cookies) and turn out thin or flat. If the recipe requires a greased pan or sheet, our Test Kitchen experts recommend using shortening, which spreads less than butter due to its higher melting point.

Here's the method:

1. Apply a small amount of shortening to a paper towel or a piece of wax paper. (Alternatively, you can use a pastry brush to spread softened shortening.)
2. Spread the shortening in a thin layer over the bottom and sides of the pan.
3. Ensure the crevices where the sides meet the bottom of the pan are well-coated.

Andy Lyons

3. Line Your Pan or Cookie Sheet
Whether your recipe requires a greased pan or not, you can line your pan or cookie sheet with foil, parchment paper, or a silicone baking mat. Using foil or parchment paper allows you to lift the entire batch of bars from the pan at once when it's time to cut them.

To create a foil liner:

1. Tear off a piece of foil that is larger than the pan (leave extra length for overhang on either end) and shape it over the outside of the pan, folding the foil at the corners.
2. Carefully lift the foil off the pan and turn the pan over. Fit the shaped foil into the pan, leaving the overhang as "handles" to lift the recipe out of the pan. If the recipe specifies a greased pan, ensure you grease the foil as you would the pan.

Blaine Moats

4. Allow Sufficient Cooling Time for Your Cookies
Adhere carefully to the cooling instructions provided in the recipe. Bars usually cool in the pan on a wire rack. Some cookies require cooling for a few minutes on the cookie sheet before being transferred with a spatula to a cooling rack. With adequate cooling time, both cookies and bars will firm up properly.

5. Remove Your Cookies or Bars with Care
If you grease your pan, you can cut the cooled bars into squares or diamonds. Then use a thin metal spatula to loosen the bars around the edges of the pan. Use the spatula to gently lift the bars from the pan. If you used a foil liner, use the overhang to lift the bars (foil and all) from the pan; cut the bars into squares or diamonds. Gently lift each bar from the foil, pulling down on the foil as necessary to remove it from the bottom of the bars.
Once you've removed the cookies, let the baking sheet cool and use a spatula to remove any crumbs. Alternatively, rinse the cooled baking sheet with cool water and dry thoroughly. Make sure the cookie sheet is cool, clean, and dry before using it for another batch to prevent the dough from spreading before it bakes.