Cook the penne pasta according to package instructions. Drain and set aside.
In a large skillet, heat olive oil over medium-high heat. Add thinly sliced beef and cook until browned. Remove from skillet and set aside.
In the same skillet, add bell peppers, mushrooms, and minced garlic. Sauté until vegetables are tender.
Return the beef to the skillet, add Cajun seasoning, and stir to coat everything evenly.
Pour in the heavy cream and bring the mixture to a simmer. Continue to cook for 2-3 minutes until the sauce starts to thicken.
Add the cooked penne pasta to the skillet, tossing to combine and heat through. Season with salt and pepper to taste.
Serve hot and enjoy your Cajun Beef Pasta with Vegetables.