Season beef with salt, pepper, and oregano.
Warm oil over medium high heat on a large plan.
Sear seasoned beef on both sides until a beautiful brown sear color occurs (about 3-4 minutes per side).
Remove beef and set aside.
Into the same pan, add onions and saute until softened, about 3 minutes. Add in garlic, and cook an additional 30 seconds.
Place onions and beef and remaining ingredients into a slow cooker. Close with lid and cook on high for 3-4 hours or low for 6-8 hours.
Once beef is cooked, remove beef and set to the side. Drain sauce over a colander into a large bowl. The juice left over is the au jus that can be thickened. (Note below.)
Shred beef and return to the slow cooker with some of the au jus to keep moist.
To assemble sandwiches, place cheese into the inside of a hoagie roll and toast in the oven over 450 degrees for a few minutes, or until cheese melts.
Top hoagie rolls with shredded beef.
Serve with au jus to dip into.
Serves: 8-10 sandwiches