Heat oil over medium heat in a 10-inch nonstick skillet. Once hot, add the garlic and saute just until fragrant. Working quickly so the garlic doesn't burn, add egg mixture and cook for 7 to 8 minutes, without touching it, until the edges begin to brown. Using a spatula, slide the frittata onto a large plate. Invert back into the skillet and continue to cook until firm and cooked through, about 5 minutes. Cut into wedges and serve warm.