Swiss Chard and Sausage Frittata

<p>Extra Virgin Olive Oil<br /> 1 pound Spicy Italian Sausage (removed from casing)<br /> 1 Red Onion (thinly sliced)<br /> 3 cloves Garlic (minced)<br /> 2 bunches Swiss Chard (chiffonade; thinly sliced)<br /> 8 Eggs&l