Note for Windows users: the QuickTime player on Windows requires subtitled outputs to have the .m4v extension. So, to watch encoded videos with subtitles on QuickTime, you need to change the extension of the file, e.g., Bio_1.mp4 -> Bio_1.m4v .
If subtitles are not on by default, go to the View menu, click on Subtitles and choose English (or the name of the language your subtitles track is on). This is valid for QuickTime on both Windows and Mac:
If you want to make the subtitles show by the default, then go to the Edit menu, choose Preferences and click on Player Preferences. On the General tab, check the Show closed captioning when available and the Show subtitles when available boxes. Then click Apply. Next time you open QuickTime, you should be able to see captions or subtitles automatically.
Appearance Settings on QuickTime Pro:
Note for Mac users: the following instructions are only valid for QuickTime 7 Pro.
On QuickTime Pro, you can change the Horizontal and vertical placement, Width and Height of the subtitle pane by going to Window -> Show Movie Properties. On the Properties dialog box, click on the Subtitle Track, and then the Visual Settings tab. To change the vertical placement, you need to enter a different value on the second box, next to Offset. For example, to place the subtitles at the top of the screen, you need to enter 0 (pixels).
To keep the changes you made, go to File -> Save -> Save as a self-contained movie. This will preserve the changes you made to the Subtitles track.