Cook bacon and onion over medium-high heat until bacon is fully cooked. Drain.
In large bowl, combine bacon, onion, radishes, eggs, cheddar, ricotta, and Swiss cheese.
Pour mixture into greased 9x13-inch casserole pan.
Bake at 350°F until eggs are set (about 45-50 minutes).
Turnips could be used in place of the radishes if desired.Leftover ham can be used in place of or in addition to the bacon.Cottage cheese is a great sub for the ricotta cheese. Sour cream or yogurt may work too.