Brisket baked beans can be made a slow cooker, crock pot or Dutch oven inside a conventional oven. If using a Dutch oven, preheat the oven to 275°F.
Chop the slices of bacon into ¼-inch pieces. Place the chopped bacon in a large Dutch oven. Cook over medium heat, stirring occasionally, until the bacon fat renders, about 6 minutes.
Add the onion, poblano pepper, red bell pepper, jalapeño peppers and garlic to the cooked bacon. Stir to combine. There is no need to remove the bacon grease. Cook, stirring occasionally, until the vegetables have softened, about 7 minutes.
If using a slow cooker or crock pot, transfer the bacon and vegetable mixture to the slow cooker.
Add the remaining BBQ sauce, brown sugar, beer, molasses, tomato paste, mustard powder, kosher salt, black pepper and cayenne pepper. Stir to combine.
Drain and rinse the beans under cold water. Place beans in with the bacon and vegetable mixture. Add the chopped brisket and stir to combine.
Place the Dutch oven inside the preheated oven, uncovered, and cook 2 hours until the sauce thickens. If using a slow cooker or crock pot, cover and cook on low heat for 6 hours or until the beans are tender and the flavors have combined. Stir occasionally.
Serve the Brisket Baked Beans as a tasty side dish alongside your favorite BBQ meats, hot dogs, potato salad, or macaroni salad.