The ideal temperature for keeping food warm in the oven until it is time to serve is between 140 degrees and 165 degrees Fahrenheit. Since harmful bacteria can grow when the temperature in the oven falls under 140 degrees, keeping food in the oven at the appropriate temperature until serving can help stave off food-borne illnesses and bacteria that cause food poisoning.
According to the CDC, once food has been served, it should be left out for a maximum of two hours at room temperature. After that time threshold, any foods left over should be discarded. When eating outdoors, especially when the temperature is hot, unchilled food should be thrown out after an hour.