1Pat the beef chuck roast dry and season generously all over with salt and black pepper.
2Layer half the sliced onions on the bottom of the slow cooker.
3Place the seasoned roast on top of the onions.
4Arrange the remaining onion slices over the roast.
5In a small bowl, whisk together the beef broth, pepperoncini brine, oregano, garlic powder, onion powder, and bay leaves. Pour this mixture over the roast.
6Scatter the pepperoncini peppers evenly over the top, then dot with butter pieces.
7Cover and cook on low for 7 to 8 hours, or until the meat is fork-tender and shreds easily.
8Using tongs and a slotted spoon, transfer the roast and onions to a serving platter.
9Skim any excess fat from the cooking liquid, then pour the broth and peppers over the roast.
10Discard the bay leaves. Serve hot over mashed potatoes, egg noodles, or crusty bread.