In a large bowl, use clean hands to mix together all the ingredients except the oil.
Form the mixture into four patties, each of them about 4 ounces in weight, 3.5 inches in diameter, and ½ inch thick.
Preheat a grill or a grill pan on medium-high heat. Lightly brush the grill with oil.
With your thumb, make a slight depression in the center of each patty, to help the hamburgers cook evenly and maintain their shape.
Cook the hamburgers, dimpled side up, for 4 minutes. Turn and cook them on the other side, about 3 more minutes for medium doneness. This is a rough guideline. How long you need to grill will ultimately depend on how hot your grill is, on the thickness of the patties, and on your desired level of doneness.
If you'd like to make cheeseburgers, you can top each burger patty with a slice of your favorite cheese during the last minute of grilling. Cover the grill or the grill pan so that the cheese can melt. Alternatively, finish cooking the burgers, top them with cheese, and briefly microwave them to melt the cheese, about 30 seconds for 4 burgers.
Consuming undercooked meat may increase your risk of foodborne illness. The USDA recommends cooking ground meats to 160°F.