In MLA format, when I'm citing multiple pages from a source, do I list them all in the in-text citation?
Yes. This applies both to situations where you are referring to material from a source and when you are including direct quotes from a source.
For instance, if you were citing this passage which appears on pages 26-27 of a book by an author with the last name Russell:
From its birth in the late nineteenth century, progressive education has wrestled with the conflict within industrial society between pressure to increase specialization of knowledge and of professional work (upholding disciplinary standards) and pressure to integrate more fully an ever-widening number of citizens into intellectually meaningful activity within mass society (promoting social equity).
You would include both 'Russell' and '26-27' in your citation, as in this example:
Progressive education has always involved conflict between upholding disciplinary standards and promoting social equity (Russell 26-27).
If you directly quoted the source, you would also include the author and both page numbers.