Season roast with steak seasoning. Heat olive oil in skillet over medium to medium-high heat and brown tri-tip approximately 4-5 minutes each side. Place fat side up in slow cooker crock.
Saute onion and garlic in skillet about 4-5 minutes, add peppers and continue cooking a few minutes until fragrant. Add to crock.
Add beer and tomatoes to crock. Cook on low 8 hours.
Remove meat and allow to rest 10 minutes before shredding and returning to sauce. Serve with rice and/or beans or use as a filling for tacos, burritos, enchiladas or tamales.