Bring a large pot of water to a boil. Add the pasta shells and cook until al dente. Drain and set aside.
While the pasta is cooking, add the olive oil to a large skillet over medium heat. Add the onion, saute 3-4 minutes, add the garlic and saute for an additional minute.
Add the ground beef and cook through. Drain any grease from the ground beef, then add the enchilada sauce and cooked pasta to the skillet.
Reduce heat to low and simmer 3-4 minutes.
Sprinkle the cheddar cheese on top, cover and allow the cheese to melt, 1-2 minutes.