How can I apply for researches in the medical field in foreign countries after MBBS degree?

You're supposed to give GRE followed by TOEFL or EILTS. EILTS and TOEFL depend on the preference of the country. TOEFL is for US and Canada. EILTS is for UK, Australia and New Zealand. GRE is the standardised test and TOEFL/EILTS are language exam.

You will have to check the eligibility of respective institutes you would like to take admission in and if you will be eligible for doing a research then you can apply by covering up all the necessary requirements there will be definite chance of interview if you will apply for research in any reput