Gather all ingredients.

Bring a large pot of lightly salted water to a boil. Add penne and cook, stirring occasionally, until tender yet firm to the bite, about 11 minutes.

While the pasta is cooking, cook bacon and onion in a large skillet over medium heat, stirring often, until bacon is crisp and onion is beginning to brown, about 10 minutes.

Remove from the heat and drain grease into a small container.

Drain pasta and transfer to a large serving bowl.

Add oil and stir to coat pasta.

Add cooked bacon and onion plus 1 to 2 tablespoons bacon grease.

Sprinkle Parmesan over pasta and stir until well combined. Add more bacon grease as desired for flavor and moisture.