Add the olive oil to a large, high-sided skillet over medium-high heat. Once hot, add the onion, yellow squash, and zucchini and saute until tender, about 5 minutes. Season with salt and pepper. Add the cranberries and chicken broth and bring to a boil. Stir in the couscous, cover with a tight fitting lid, turn off the heat, and let sit for 10 minutes.
Remove the cover and fluff with a fork. The couscous can be served hot or at room temperature.