You should always acknowledge when a speech was accessed using a secondary source. Thus, how you cite a copy of a speech depends on where you found it and the form in which it appears.
Republished in a Digital Book
To cite a speech republished in a digital book, follow the MLA format template. List the name of the speaker and the title of the speech. Then list the title of the book and—if given—its editor, followed by the publication details for the book. If the work exists in print as well, list the format in the “Version” slot so that your reader will know that you are citing the digital version:
Note that you do not need to provide original publication information for the speech because you are not citing the original version. You are citing the version republished in a book.
Scanned and Housed on a Web Site
If you cite a speech from an archive scanned and housed on a Web site, you should list the original publication details provided by the site. The speech document is simply housed on the Web site; it is not a republished version of the work. The works-cited-list entry below, for a speech by Dwight Eisenhower scanned and housed on the Web site Docsteach, lists the name of the speaker and the title of the speech. The date of the speech is given in the middle optional-element slot because it refers back to what precedes. The name of the collection containing the speech is given as the title of the container, followed by the location of the collection. The second container lists the name of the Web site, its publisher, and the URL:
Republished on a Web Site
If a speech is republished in an HTML version on a Web site, then cite the speech the same way you cite a speech republished in a book. The Docsteach site from the example above contains not only a scan of Eisenhower’s speech but also an HTML transcript. To cite this version of the speech, list the name of the speaker, the title of the speech, and—in the middle optional-element slot—the date of the speech. Then list the name of the Web site as the title of the container, followed by the publication details. For clarity, you might list the format in the optional-element slot at the end of the entry.
Note that in the book example, the date of the publication is that of the book rather than that of the speech because it is the most relevant date for that version of the work. In the transcript example, the date of the speech is provided because it is provided on the transcript.
Read more on citing speeches—in particular, a lecture or speech heard online.