In a shallow skillet over medium heat, brown the ground beef until all the fat is rendered and no pink remains. Drain well. Set aside.
In the same skillet, add the oil. Once hot, add the onion and bell pepper. Sauté until beginning to soften. Add the garlic and stir for about 30 seconds. It should begin to smell very fragrant.
Lower the heat to medium-low, add the taco seasoning and tomato paste. Stir until the tomato paste begins to darken, approximately 2 to 5 minutes, depending on your heat source.
Add the canned tomatoes, pasta, and beef stock. Bring the mixture up to a boil. Lower the heat to a simmer. Taste the broth and see if you need to add any seasonings. It will be hot, so be careful. This liquid needs to be very flavorful because the orzo will be absorbing it.
Cook the orzo, stirring often, until al dente, approximately 10 to 12 minutes. If you notice the pasta is not done cooking, and the mixture is too dry, add more stock, about a quarter cup at a time. Continue to stir often until the pasta is finished cooking. (Please, see Notes below for cooking times in relation to brands of pasta.)
Add the drained ground beef, beans, and corn (if using) to the orzo, stirring to thoroughly combine.
Taste the mixture and adjust any seasoning as needed.
Serve in individual bowls, topped with desired toppings.