Quarter each of the summer squash and/or zucchini lengthwise and then slice the quarters into 1/4 inch slices. Roughly chop the onion into slices about the size of your squash slices.
Combine all the summer squash in a medium bowl with 2 tablespoons olive oil, 1 and 1/2 teaspoons Simply Organic Tuscan Seasoning, and 1/2 teaspoon salt. Mix until the olive oil, Tuscan Seasoning and salt are evenly distributed over the vegetables.
Heat a stainless steel skillet over medium heat. Add the vegetables and cook for about 10 minutes, stirring occasionally, until all the vegetables are softened and beginning to brown.
Meanwhile, cook the spaghetti in boiling water according to the package directions. Drain and set aside when finished.
When the vegetables and spaghetti are both ready, distribute the pasta on plates, top with 1/4 of the vegetable mixture and finish with 2 tablespoons crumbled feta cheese each.
Serve and enjoy!