One of the reasons cooks enjoy cooking hamburger patties in panini presses is because the cooking time varies from five to ten minutes, depending on the manufacturer. Because panini makers preheat more quickly than coal grills, for example, cooking hamburgers on a panini grill is often quicker than traditional grilling. If you need to defrost your hamburger patties, however, you may feel like you aren't saving much time at all, since defrosting from frozen can take several hours without the aid of a microwave.

There are several drawbacks of not thawing your frozen burger patties before cooking on a panini grill. Manufacturers base their estimated cooking times off of thawed or fresh meat; using frozen meat means that manufacturer instructions for cooking times are inaccurate, increasing the risk that you may under or overcook your meat. Since frozen meat takes longer to cook than thawed meat, using a panini maker instead of a grill or skillet may not save you much time at all. Another consideration is the impact excess water will have on the taste and texture of your finished burger.

Aside from the cooking risks, some panini grill manufacturers expressly warn against cooking any frozen foods on their grills. Casera, for example, notes in their panini maker user guide that, "All food must be fully and completely defrosted before cooking." Other manufacturers, though they do not expressly forbid cooking frozen beef patties, provide instructions only for cooking fresh or defrosted burger. If your panini maker user guide expressly advises against cooking frozen meats, do not attempt to cook your burgers patties frozen.

If your panini manufacturer suggests using fresh or thawed burger patties, run your frozen patties through the defrost cycle in your microwave first, or microwave them in 30 second increments until they are no longer frozen. Follow the manufacturer instructions for heating burger patties on the panini; some panini grills advise using an open grill while others provide instructions for closed grill cooking. If you are using frozen patties instead of thawed, you cannot rely on the manufacturer guidelines for cooking times. Instead, use a cooking thermometer to ensure that the internal temperature of your burger patties reach 160 degrees Fahrenheit, the minimum temperature for food safety according to the US Department of Health and Human Services. Insert the thermometer in the side of one patty to the center; if the thermometer cannot penetrate the frozen meat, cook the burgers until the meat is soft enough to slide in the thermometer probe, and then continue cooking until the temperature reads 160 degrees or above.