You may download, save and print the .PDF manual free of charge from:
This .PDF document does not specify it as the Model 5811 manual; however, it is nearly identical, right down to the control panel on top.
Before I posted this comment, I downloaded, saved and printed the .PDF manual, and then took it downstairs to give it a whirl. PERFECT! At the time of this writing, my elderly Oster Bread Machine, Model 5811, #BM-100 (J222) is whipping up my first large loaf of white bread!
Incidentally, we discovered our Oster Bread Machine sitting on a shelf in an old house we were given as an apartment community manager quarters. It was sitting with some other stuff slated to be hauled to Goodwill (or the dump)!
I spent the past hour surfing the net looking for an Oster Bread Machine Model 5811 manual. Other than a couple of site where I was asked to pay a fee to download a .PDF or .ZIP file, there was little else. A couple of sites that purported to be THE place to download the manual turned out to be non-existent or otherwise dead ends.
Hope this helps all you who have been seeking this manual in vain for so long.