You can hardly blame a guy for cooking a little chili in his room ("Up in Barney's Room," Episode #104) - especially when he's not allowed to use more that a 40-watt bulb and he leaves a clean wash basin. After all, for six dollars a week in rent, a man should have some privileges.
Actually, Mrs. Mendelbright really is a sweet landlady (bless her heart) and she is a good friend to Barney. By the way, the dresser that Barney uses as an oven and kitchen counter belonged to Mrs. Mendelbright's mother. It was shipped all the was from Ft. Lauderdale.