Cook green beans in boiling water to cover 5 minutes or until crisp-tender; drain and set aside.
Place butter and olive oil in a large skillet over medium-high heat until butter melts and oil is hot. Add onion, and sauté until tender. Reduce heat to medium; add oregano, and sauté 1 minute.
Add green beans, and cook, stirring often, 5 to 8 minutes or until tender. Toss with salt and pepper.