Set the Instant Pot to ‘Sauté’ mode and heat the olive oil.
Add the diced onion and cook for 2-3 minutes until softened.
Add the minced garlic and cook for 30 seconds until fragrant.
Add the ground beef and cook, breaking it apart with a spoon, until browned and no longer pink, about 5-7 minutes.
Drain excess fat if necessary.
Add the diced red bell pepper, diced carrots, frozen peas, diced tomatoes with their juice, beef broth, tomato sauce, dried oregano, dried basil, salt, and black pepper to the Instant Pot. Stir to combine.
Add the uncooked elbow macaroni and stir gently to submerge the pasta in the liquid.
Secure the Instant Pot lid and set the valve to ‘Sealing’.
Select ‘Manual’ or ‘Pressure Cook’ mode and set the timer for 5 minutes.
When cooking is complete, allow the pressure to release naturally for 5 minutes, then carefully perform a quick release to release any remaining pressure.
Open the lid and stir the casserole well.
Sprinkle the shredded cheddar cheese evenly over the top, close the lid (do not seal), and let it sit for 3-5 minutes until the cheese melts.
Serve hot.