Begin by preheating your oven to 350°F (175°C) to prepare for baking the frittata.
In a large skillet, pour in the olive oil and heat it over medium heat. Once the oil is hot, add the diced potatoes. Sauté the potatoes for about 8-10 minutes, stirring occasionally to ensure even cooking, until they start to soften and turn slightly golden.
Next, incorporate the diced red and yellow bell peppers into the skillet. Continue to cook for an additional 5 minutes, stirring frequently, until the peppers are tender and fragrant.
Add the chopped spinach to the skillet, stirring it in until it wilts, which should take about 2 minutes. Then, sprinkle the garlic powder, salt, and pepper over the mixture, stirring well to combine and infuse the flavors.
In a separate mixing bowl, whisk together the eggs and milk until smooth and well combined. Pour the egg mixture evenly over the sautéed vegetables in the skillet, ensuring it covers everything.
Evenly distribute the shredded cheese on top of the egg and vegetable mixture. Allow the frittata to cook on the stovetop for about 3-4 minutes. Watch for the edges to begin to set – this will help create a nice base for the frittata.
Carefully transfer the skillet to the preheated oven. Bake the frittata for 15-20 minutes, or until it is puffed up and the center appears set. To test for doneness, insert a knife into the center; it should come out clean.
Once the frittata is fully cooked, remove it from the oven and let it cool for a few minutes before slicing it into wedges for serving.
Notes
Serve warm, garnished with fresh parsley for added color.