Chop and peel onions and mince the garlic cloves.
Season beef with salt, pepper, and oregano.
Warm oil over medium high heat in a large skillet.
Sear seasoned beef on both sides until a beautiful brown sear color occurs (about 3-4 minutes per side).
Remove beef and set aside.
In the same pan, add onions and saute until softened, about 3 minutes. Add in garlic, and cook an additional 30 seconds. Place thyme sprigs on top
Place onions and beef into a slow cooker. Add the beef broth, Worcestershire sauce, soy sauce and beer Place the lid on 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 submarine rolls with shredded beef.
Serve with au jus to dip into.