Pork Chops are pretty cheap and good when trimmed.
The ultimate fill you up, taste good, healthy for you food are, of course, beans (which includes stuff like lentils and what not). Not freaking sugared up baked beans , but beans as part of a dish of course. Sensible chilis, bean-based soups, and other dishes have long been a diet's best friend because of the way that they make you full, provide protien without the red meat, and work well in a variety of dishes.
When my wife goes on her trips in the field over the spring/summer, I make some chili or a bean soup and just eat it until she comes back. Quick, never hungry, and its easy so doesn't get in the way of my reading/gaming.
Just drink lots of WATER to keep them digesting. No one at work wants to listen to your frequent colonic disruption.