Q. How long can quotations be in an MLA style research paper?

There are no official limits to quotation length, though any quotations that are more than four lines should be formatted as a separate block quote.  However, it is generally better to paraphrase the sources you cite rather than use direct quotations.  Excessive use of direct quotations can make it look like you do not fully understand the material you are using, while paraphrasing shows a better grasp of the material and makes your paper appear more like a unique work.  The link below offers some useful advice about finding a good balance between direct quotes and paraphrasing.

COM's Tutoring Center can also help you with writing a research paper.  You can learn more about it through the second link.