MOSCOW, Dec 10 (Reuters) - Russia is considering imposing a grain export quota and wheat export tax amid rising domestic food prices, three sources familiar with discussions at the government told Reuters. The quota and the tax could be imposed for Feb. 15-June 30, two of the sources added. Prime Minister Mikhail Mishustin said earlier on Thursday Russia would prepare measures to stabilise domestic food prices, a day after President Vladimir Putin criticised officials and market players over rising prices for bread, flour, sugar and sunflower oil. (Reporting by Olga Popova and Polina Devitt; additional reporting by Darya Korsunskaya; editing by Mark Potter)