In a large nonstick skillet, heat oil over medium heat. Add shallot, and cook, stirring, until translucent, 3 to 5 minutes. Add mushrooms, and cook until tender, 8 to 10 minutes.
Add 3/4 cup water and green beans. Season with salt and pepper, stir to combine, and reduce heat to low. Cover, and cook until beans are crisp-tender, 7 to 10 minutes. If any liquid remains, raise heat, and cook until it evaporates.