The first thing you probably noticed is how vague this recipe is and there's a good reason for that. This recipe is the easiest way to use up leftovers into a one-dish delicious breakfast or brunch meal. Use what you have and don't be afraid to push the boundaries of what "normal" looks like for you.* Here's my basic recipe (it's different every time).
Preheat oven to 400
In a large oven-safe skillet, warm a little bit of Vegetable Oil over medium high heat. Cook any meat that isn't pre-cooked (Sausage, Bacon) with your heartier Veggies (onions, peppers, zucchini, etc). Sautee until fork tender. Add in any "softer" or "pre-cooked" veggies (leftover baked potatoes, cabbage, olives, spinach). Sautee slightly (I judge by when my spinach starts to wilt - I ALWAYS use a lot of spinach!!!)
While Veggies are cooking, whip your eggs together in a medium bowl. Add milk and seasonings just like you would for scrambled eggs.
Stir Eggs and Grated Cheese into Veggie Mixture. Place in preheated oven and cook for 35-45 minutes. Frittata is done when eggs are firm to the touch in the center of the pan and edges are browned.
You can top with a little more grated cheese and stick back in the oven for 2-3 minutes if you like.
Serve warm and enjoy! You can eat it as it is, or a fun variation is to warm flour tortillas and make burritos out of the Frittata.
*Some of my best combinations were literally digging through the fridge and seeing what needed used. A favorite was a ton of vegetables including leftover grilled asparagus with meat I salvaged out of a family size Italian Salad from the night before (pepperoni, salami). Another time I found some bbq'd steaks that got moved to the back of the fridge (yeah I don't know how either) so I rinsed the bbq sauce off and used those with chopped up frozen fries because I was out of potatoes. I love how versatile this recipe is and how creative and weird you can be. I've never had a bad Frittata.