Bring a large pot of salted water to a boil. Add the pasta and cook according to package instructions until al dente. Reserve 1 cup of pasta water, then drain the pasta and set aside.
In a large skillet, heat the olive oil over medium heat. Add the diced onion and sauté for about 3-4 minutes until translucent.
Stir in the minced garlic and cook for an additional 1 minute until fragrant.
Add the diced zucchini, yellow squash, and bell pepper to the skillet. Sauté for about 5-7 minutes until the vegetables are tender.
Add the cherry tomatoes, dried oregano, salt, and black pepper. Cook for another 3-4 minutes until the tomatoes begin to soften.
Combine the cooked pasta with the sautéed vegetables in the skillet. Toss to combine, adding reserved pasta water a little at a time until the desired consistency is reached.
Remove from heat and stir in the fresh basil, grated Parmesan cheese, and lemon juice. Mix well and serve immediately.