Preheat the oven to 350°F (175°C).
Heat olive oil in a large skillet over medium heat.
Add diced onion and red bell pepper to the skillet and sauté for 4-5 minutes until softened.
Add ground beef to the skillet and cook, breaking it apart with a spatula, until browned and fully cooked, about 7-8 minutes.
Drain excess fat from the skillet and season the beef mixture with salt, black pepper, garlic powder, and dried oregano. Stir to combine and remove from heat.
In a large mixing bowl, whisk together eggs and whole milk until smooth.
Grease a 9×13 inch baking dish with cooking spray or a little olive oil.
Spread the cooked ground beef and vegetable mixture evenly in the bottom of the baking dish.
Sprinkle shredded cheddar cheese evenly over the beef mixture.
Pour the egg and milk mixture evenly over the cheese and beef layer.
Bake in the preheated oven for 35-40 minutes, or until the egg is set and the top is lightly golden.
Remove from oven and let cool for 5 minutes before slicing and serving.