In a large skillet over medium-high heat, add the Italian sausage. Cook for 3-5 minutes, breaking it apart with a spatula until browned and cooked through.

Lower the heat to medium and add a drizzle of olive oil. Sauté the chopped onion and bell peppers for 3-5 minutes until they start to soften.

Stir in the grape tomatoes and cook for about 5 minutes, allowing them to soften.

Increase the heat back to medium and add the pepperoni slices, cooking for about a minute until crispy.

Return the browned sausage and sautéed vegetables to the skillet with the pepperoni. Pour in spaghetti sauce and mix in the cheeses until melted.

If oven-safe, switch to broil and top with mozzarella for 1-2 minutes until melty and golden.

Serve topped with crispy pepperoni, Italian seasoning, and fresh basil.