Preheat the oven to 350°F. Coat a standard-sized muffin pan with cooking spray. Be sure to coat the pan really well so the egg bites don't stick when you remove them.
Whisk the eggs, cheese, chives, salt, and pepper in a large bowl. Fill each muffin mold about 3/4 full with the egg mixture. The chives have a tendency to float on top of the mixture in a cluster. If this happens, gently spread them out with a spoon.
Bake the egg bites for 20 to 25 minutes or until they are set in the middle and the edges have pulled away from the pan. You can also use a toothpick to check insert it into the middle of an egg bite - it should come out clean.
Cool the egg bites for a couple of minutes in the pan before removing them. They will shrink as they cool.
Notes
You can store them in the refrigerator for up to a week or in the freezer for several months. Whichever you choose, I recommend lining the storage container with a paper towel to absorb excess moisture.I reheat egg bites in the microwave at 50% power. This warms them slowly so they don't get rubbery. You can reheat them from frozen - no need to thaw first.You can enjoy them as is, but I like to use them to make breakfast sandwiches. Toast an English muffin, warm up the egg bite (or two), and add a slice of cheese.