Rainbow Pepper Saute

Heat oil in a large nonstick skillet over medium heat. Add onions and cook, stirring often, until softened, 3 to 5 minutes. Add peppers; cook, stirring occasionally, until softened, 7 to 10 minutes. Stir in oregano, salt and pepper; cover. Cook, stirring occasionally and adjusting the heat as necessary so the mixture doesn't burn, until the peppers are very tender, 15 to 20 minutes. Serve warm or at room temperature.