Preheat oven to 350°F with rack in lowest position. Stir together beer and brown sugar in a large oven-safe high-sided skillet. Add ham; bring to a boil over medium-high. Reduce heat to medium-low; simmer 10 minutes, turning ham occasionally.
Transfer skillet to preheated oven; roast until a thermometer inserted in thickest portion of ham registers 110°F, 1 hour to 1 hour and 30 minutes, turning ham every 20 minutes.
Continue roasting at 350°F, without turning, until a thermometer inserted in thickest portion of ham registers 145°F, 30 minutes to 1 hour, basting ham with beer mixture in skillet every 10 minutes.
Transfer ham to a serving platter; tent with foil to keep warm. Return beer mixture in skillet to heat over medium; cook, stirring often and skimming fat if needed, until thickened, syrupy, and reduced to about 1 cup, about 5 minutes.
Untie ham; brush with ¼ cup beer glaze. Serve ham hot alongside remaining ¾ cup glaze.
