In a large skillet, heat 3 tablespoons of oil over medium heat. Add the sliced carrots to the pan and season with salt and pepper. Sauté until cooked through, stirring regularly. Transfer to a plate and set aside.
In the same skillet with the remaining tablespoon oil, add sausage and cook for 5 minutes over medium heat and set aside.
Add bell peppers and stir-fry until crisp-tender, about 2 minutes. Set it aside.
Still in the same pan, add garlic and onion and season with Italian seasoning, salt, and pepper. Stir-fry until onions are translucent then deglaze with 1/4 cup stock.
Add the sauteed carrots, bell peppers, scallion, and sausage back to the skillet and mix everything together. Cook for 2 to 3 minutes more and stir well to coat the sausage and veggies with the sauce.
Adjust seasoning if needed, garnish with chopped scallion and serve.