- Coat bottom of 9- or 10-inch heavy-bottomed saucepan with oil and place over medium-high heat.
- Add half the onions and half the baby carrots and cook, stirring often, for 7 to 10 minutes. (Although vegetables won’t brown evenly, they will get some color.)
- Add half the zucchini and half the pattypan squash.
- Cook, stirring often, until vegetables just begin to soften, about 5 minutes.
- In small cup, mix 2 tablespoons red wine vinegar with 2 tablespoons vegetable stock and add to vegetables.
- Shake pan or stir vigorously while liquid evaporates.
- Reduce heat to medium, add ¼ teaspoon salt and ½ cup vegetable stock or water; cover tightly and cook for 10 minutes.
- Repeat process with second batch.
- To serve, add freshly ground pepper and garnish with chopped parsley.