Place the bacon in a large, deep skillet and cook over medium heat, turning occasionally, until evenly browned and crisp, about 15 minutes. Remove the bacon to cool, leaving the drippings in the skillet.

Stir the vegetable oil and flour into the bacon drippings. Cook and stir until the flour has turned nearly as brown as the bacon, about 5 minutes. Stir in the onions and cook until the onions soften and turn translucent, about 5 minutes; stir in the stewed tomatoes, breaking them apart with your spoon. Crumble the cooked bacon into the tomatoes and bring to a simmer. Reduce heat to medium-low and simmer until the gravy has reduced to your desired thickness, about 10 minutes.