How to Make It
Cook the pasta according to the package directions. Reserve ½ cup of the cooking water; drain the pasta and return it to the pot.
Meanwhile, in a large skillet, heat 1 teaspoon of the oil over medium-high heat. Add the sausage and cook, breaking it up with a spoon, until browned and cooked through, 10 to 12 minutes. Transfer to a plate.
Reduce heat to medium and add the remaining tablespoon of oil to the skillet. Add the zucchini and/or squash, onion, garlic, ½ teaspoon salt, and ¼ teaspoon pepper. Cook, tossing occasionally, until the vegetables are golden and very tender, 15 to 18 minutes (reduce heat if the pan begins to darken).
Toss the pasta with the sausage, vegetables, Parmesan, oregano, and ¼ cup of the reserved cooking water (add more cooking water if the pasta seems dry). Serve with additional Parmesan.