In a saucepot over medium-high heat, add the oil, onion and garlic; cook until the onions begin to soften. Add remaining ingredients; bring to a boil, then simmer, uncovered, for 30 minutes, stirring occasionally. Remove the sauce from heat and add the beer.
With the grill or pan on medium-high heat, place burgers down and cook for 2 minutes. Flip each burger and baste in bbq sauce; let sit for 2 minutes before flipping and basting other side. Repeat as needed until burgers are fully cooked.
Optional: Add cheese slices for ultimate summer nostalgia.