In a large bowl, whisk together the eggs with salt and pepper to taste. Set the bowl aside.
Heat a large nonstick sauté pan over medium-low heat. Add the olive oil. Once the oil is hot, add the onions and sauté them until translucent then add vegetables and cook them, stirring occasionally, until they're softened slightly. Add the spinach and pasta and cook an additional 1 to 2 minutes.
Pour the eggs into the pan and increase the heat to medium-high. Cook the mixture, lifting up the egg so that the uncooked egg flows underneath until the eggs are almost fully set. Reduce the heat to low, cover the pan and continue cooking until the eggs are fully set. Uncover the pan and turn off the heat. Sprinkle the cheese atop the frittata then cover the pan again for 1 minute (off the heat) until the cheese is melted.
Use a rubber spatula to loosen the frittata from the pan then slide it onto a serving dish. Slice into wedges and serve.