Preheat the oven to 350°F and slice potatoes into ~½ inch rounds, and then dice them into ½” cubes. Finely dice the white onion, bell pepper, and jalapeño, too.
Add the diced potatoes to the casserole dish and coat in olive oil and salt + pepper. Pop them into the oven for 25 minutes.
Remove potatoes from the oven but keep the oven on. Add ground beef mixture, canned tomatoes (drained), and ½ of the fry sauce on top of the potatoes. Stir it all together.
Serve on a bed of shredded lettuce and add remaining fry sauce. Enjoy!