Heat a large skillet over medium high heat, melt the butter.
Add the sliced zucchini, squash and onions. Saute for 5-10 minutes until starting to soften. Don't over stir, as you want to get a browned vegetable.
Add minced garlic, garlic powder and salt. Continue to saute for 15 minutes.
Add sausage and saute for an additional 10 minutes until the sausage is heated through (if using a pre-cooked sausage) and squash is fully cooked through and slightly browned. Serve.