In a large bowl, whisk the eggs, parmesan cheese and the pepper together. Set aside.
In a deep frying pan with an oven proof handle (or in the deep half of a frittata pan) warm the olive oil. Add the sausages and cook until browned and cooked through, about 5-7 minutes. Transfer to a cutting board and coin slice. Leaving only 1 tsp of oil in the pan, on medium heat add the green onions and bell pepper and cook until tender, about 2 minutes. Stir in the garlic and thyme and cook for another 30 seconds. Add the cooked sausage slices to the pan along with the egg mixture; allow eggs to set for 30 seconds. Add asiago and provolone cheese and continue to cook until the edges are just starting to set, using a rubber spatula, gently pull the edges away from the side of the pan allowing the uncooked eggs to flow underneath, about 2 minutes. Continue cooking (untouched) about 4 minutes more.
Meanwhile, preheat your oven to 375 degrees and finish cooking until the center of the egg mixture is gently firm to the touch, and the edges are beginning to golden, about 6-10 minutes. (If using a Frittata pan set the shallow half of the pan over medium low heat and brush lightly with olive oil. Place the shallow pan upside down on top of the deep pan and flip the frittata into the shallow pan. Cook covered until the frittata is set, about 6 minutes.).
Gently shake the pan to loosen the frittata and use a rubber spatula to carefully slide it onto a serving plate, cut into wedges. Garnish with fresh thyme.