Heat the olive oil in a large, deep skillet with a tight fitting lid over medium heat. Once its hot, add the onion and peppers and stir them to coat in oil. Let them cook until they start to soften up a bit, then add the zucchini and yellow squash to the pan. Pop the lid on and let it cook fairly undisturbed for 3 or so minutes. Then add the seasonings and stir. Continue cooking until the squash is your desired tenderness (I usually cook mine for 10ish minutes). Then serve it up.