Here's the balance I've struck. In Brit Lit I, I spend the 1/3 of the semester on Old English, 1/3 on Middle, and 1/3 on Early Modern. In other words, my students are 2/3 of the way through the semester before they get out of that first teeny volume. I would argue, however, that it's perfectly justifiable, if one wanted to do it as a true survey, to take all of Brit Lit I as medieval, because even that gives modern all of Brit Lit II, when it is only 1/3 of the period supposedly being surveyed.Now, my inner smartaleck tempts me to respond "It's not quantity, but quality," and my inner empiricist wants to point out that even if it's quantity, the sheer numbers of authors and texts from the invention of the printing press onward has to outweigh the Parchment Years.
Nor are our modernist colleagues offering us anything close to the same courtesy. Spend about ten minutes looking at the online syllabi of non-medievalists teaching the Brit Lit surveys, and you'll find that the norm is to teach zero medieval texts, though a good number will teach one and only one (generally Beowulf or [Canterbury Tales]). Quietly take a peek at the syllabi of your colleagues in your own department, and you'll likely find the same thing.
The only way to change these survey courses so that they actually survey the first millennium of English literature is to teach them that way. No amount of cajoling your colleagues will help. Even if they editors of the Norton & Longman Anthologies read this post, it's doubtful they'll lose any sleep.** To change this, we have to offer a proper view of what the English literary canon is -- mostly stuff written in the Middle Ages.
Nevertheless, my conscience makes me cry "Mea culpa!*"
Though I don't teach a BritLit survey course, I am an English teacher, and am a product of the Norton Anthologies, woefully underinformed in the ways of the Anglo-Saxons.
*However it translates into Old English.