Here are some helpful tips to prevent cookies from spreading:
Don’t Overbeat the Batter
Far too many recipes advise bakers to simply “Cream butter and sugar until smooth”. So many people just turn on the mixer and go check their e-mail.
When you beat butter and sugar, those little crystals of sugar create air pockets between the butterfat. The more you beat, the more air you incorporate (those trapped air pockets steam open and expand in the oven). That’s great for a nice, light cake…but not for most cookies. So when the recipe says, ““Cream or beat butter and sugar”, just mix them for about 30 seconds, until well-combined.
Use Ungreased Baking Sheets
Measure Ingredients Properly
I know this is a big duh!, but adding more liquid or less flour than a recipe indicates makes a big difference. When people tell me, “I can’t bake”, I never understand that. I mean, how difficult is “8 ounces of butter” or “3 large eggs”? It’s not like a piece of meat that you need to guess and adjust cooking times. Baking is a no-brainer.
Don’t change ingredients either. Using extra-large eggs in place of large eggs means you’ve added more liquid. Using anything other than all-purpose flour (or whatever is called for) can also be problematic.
Check Your Fat
Most butter is about 80% fat, meaning the rest is roughly 20% water. When used in a batter, that water liquefies, and voila!. You can use a ‘European-style’ butter, which has a higher percentage of fat and remains more stable when baked. Examples of this include Plugra.
Some recipes use vegetable shortening instead of butter, which is another alternative (although I don’t personally use vegetable shortening). Vegetable shortening is 100% percent fat, which means there’s little water so things stay in place better when baked (it’s why pie dough made with shortening is flakier…there’s little water to saturate and toughen the flour.)
If you choose to replace butter in your recipe with vegetable shortening, find one without trans-fats, which are now available.
Check Your Oven Temperature
Every oven is completely different. I had a someone call me at 11pm one night to tell me her Peanut Butter Cookies took 10 minutes to bake instead of 9 minutes, as indicated by the recipe. Buy an oven thermometer and check the accuracy of your oven.
If you put cookies in an oven that’s not hot enough, they’ll droop and spread before firming up.
You can find more tips at my post: Tips to Keep Cookies From Spreading
Why you should use aluminum-free baking powder (and how to make your own)