This breakdown indicates about 490lb of edible boneless meat from a 1200lb live weight steer.
That is 980 portions of 8 ounces of beef. If you ate one 8 ounce portion with each meal, eating three meals per day, it would last 326 days + 2 meals or just a few days short of 11 months. I think that I would be desperate for anything else for protein after only a couple weeks of that but I could probably force myself to do it.
I picked 8 ounces portions without too much thought, just something that might be manageable on average. Turns out that 3 eight ounces portions daily would be somewhere about 1800 calories depending upon fat content of each cut. So that leaves a very small amount of other calories from other sources to maintain typical metabolic needs.
If you add in a lot of physical exercise on a daily basis then you might could push up caloric demand enough to cover the calories from an extra portion of meat. You could then eat your huge pile o’ meat in less time.