Pat the beef tenderloin dry with paper towels.
In a small bowl, combine salt, black pepper, garlic powder, dried thyme, and dried rosemary.
Rub the seasoning mixture evenly all over the beef tenderloin.
Heat olive oil in a skillet over medium-high heat.
Sear the beef tenderloin on all sides until browned, about 2 minutes per side.
Place the sliced onion and minced garlic at the bottom of the crock pot.
Add the seared beef tenderloin on top of the onions and garlic.
Pour beef broth and red wine over the beef.
Place fresh rosemary sprigs on top of the beef.
Cover and cook on low for 4 to 4 1/2 hours, or until the beef reaches desired doneness (internal temperature of 135°F for medium-rare).
Remove the beef tenderloin from the crock pot and let it rest for 10 minutes before slicing.
Serve sliced beef tenderloin with the cooked onions and pan juices.