The Muskogee County Genealogical Society has a nice free genealogy resource for those researching ancestors who died in and around the area. The Muskogee Newspaper Death and Obituary Index spans from 1907 to present. The exception is 1907 which begins in October when Oklahoma achieved statehood. Unlike most indexes of this sort, it is compiled from not only obituaries, but also deaths reported in articles and other areas of the newspapers.
The index is organized by year. Clicking on a year will open a PDF file of that year's deaths organized by name. Entries have the name, publication date and section or page.
While the index does not give you the exact date of death for your ancestor, it can help narrow down the span of time when the death occurred. If a copy of the obituary or article is desired, you can then order it from the society for a fee.