Slice ends off the zucchini and yellow squash. Cut in half horizontal then slice each half again so you have 4 long strips. Repeat for each zucchini and squash. Sprinkle a dash of salt on top. Set aside.
Slice the end off one end of the onion and remove the outer peel. Slice the onion into thick 1/2 inch rings. Coat with oil.
Grilling or roasting vegetables
Preheat the grill to high heat and prepare the grill with oil so the vegetables do not stick. If roasting preheat the oven instead to 400 degrees F.
Blot the zucchini and squash with a paper towel to remove extra water. Add more oil to prevent sticking.
If grilling, add all the squash strips and onions to a grill on medium-high heat. When picking up the onions, try to keep them in their rings, careful they do not break apart. Cook each side about 10 minutes, checking every 5 minutes to make sure they are not burning. Once done, remove and set aside.
If roasting, add the squash strips and onions to a baking sheet. Roast for 10 minutes at 400 degrees. Flip them and cook another 10 minutes or until cooked through. Turn to a broil and broil for about 2-3 minutes to brown them. Remove and set aside.
Make the spaghetti
Cook the pasta according to package directions. Chop the prepared cooked chicken, cooked zucchini, yellow squash and onion and set aside. Dice the tomatoes and set aside as well.
When the pasta is finished cooking, remove from the heat, drain the water and rinse with ice cold water to prevent further cooking. Transfer the cooked noodles back to the drained pot and add the marinara sauce. Mix well and heat on low heat.
Add the cooked and chopped chicken, vegetables and freshly diced tomatoes to the pasta. Mix well and cook until heated through. Serve garnished with fresh basil.
To make this a 30 minute dinner:
Roast or grill the vegetables in advance. Then they are ready to chop and quickly heat with the pasta.