Add ground beef and diced onion to a large skillet over medium-high heat and cook, breaking up, until browned and onion is tender. Add garlic and cook for an additional 1-2 minutes.
Drain excess grease and transfer meat to a 6- quart slow cooker.
Add remaining ingredients to the slow cooker and stir to combine. Cover and cook on low for 6-8 hours.
Remove bay leaves and stir to combine. Serve over pasta or as desired.
Notes
Serve over: Pasta, zucchini noodles, spaghetti squash noodles, etc. (not included in nutrition information)