I've actually researched the question of why Osage County is a gap in development:
1) The Osage were seen as more hostile to white settlement, even into the 1900s.
Purportedly intentionally so - to the extent that they sought out land that was unsuitable for white farming techniques (250k/1.5mil arable land in Osage County). They'd been moved too many times, and wanted to avoid it again. From their perspective, more white people = more chance of the tribe being removed . So get land they don't want and discourage development. (or so the story goes, this is more legend than fact)
The real difference is highlighted by the fact that the Osage Nation purchased the land in 1870, they were not residents on land held in trust for them by Uncle Sam (like everyone else). So for a long time the tribe controlled the land outright with few areas set aside for platted cities, they had leeway under the Dawes Act. Allotment of tribal land did not happen in Osage County until 1906 and wasn't finished until 1909. The allotments were 660 acres (as opposed to 160) and many allotments were not homesteaded, so ranchers were able to grab huge tracks of land much easier than other parts of the state.
That control was central to their identity and certainly contributed to development difficulties early on (or helped, depending on ones perspective). Control of their land remains a strong belief among the Osage today, even though most has been transferred out of the families in fee long ago (hence the belief they maintained their reservation rights, a lawsuit that came down more to "status quo" and practicality than legality as I understand it. Legally, the Osage may have been right, but it would have undone 140 years of land transactions and development).
As mentioned, the tribe retained all mineral rights, all leasing had to go through the tribe - as a result, things got ugly as wildcaters extorted, blackmailed, and murdered tribal members to gain access - leading to even more hesitancy to develop during the boom of the 1920s (it got so ugly that Congress passed a law saying headrights couldn't be inherited by a non Osage).
The effect of these factors is easily demonstrated by a looking at a map even today. Tulsa, Bartlesville, and Ponca City all ring Osage County, yet the County remains without a strong economic center. The major roads all avoid Osage County. Even the rural road network in Osage isn't up to par with most other Oklahoma Counties. Development avoided the political uncertainty of Osage County.
http://www.okhistory.org/publications/enc/entry.php?entry=OS0042) The terrain is not as friendly to development. South represented the Glenpool, flat open territory, and easy river crossings. North was hilly, had bluffs along the river, and had less easily accessible oil early in the development of the area (particularly with the Nation holding rights), oil didn't boom outright in Osage County until the 1930s (which is when the population peaked at 47k, and has never reached that level again). Even the transportation networks were designed to ferry people east and west, and south... another factor discouraging development in Osage County.
3) POLITICS. According to the Tulsa City Council's "A History of Annexation" development outside of Tulsa County was avoided by the City of Tulsa for a long time to avoid having other County Commissioners interfere with tax rates, budgeting, roads, etc. The City of Tulsa didn't annex anything outside of Tulsa County until 1973. Keep in mind, suburbs barely a thing in Tulsa even in 1973 --- Broken Arrow had a population under 15,000 people. NOT being part of Tulsa really hindered development.
http://www.tulsacouncil.org/media/79331/Annexation%20History.pdf4) Race. In 1973 when the city began annexing sections and developments started to grow in Osage County, the trend was well underway of white people moving away from the core of the city. North Tulsa, Turley, and Gilcrease Hills remain overwhelmingly black to this day. Once that trend got started in those areas, development stalled and hasn't really started back up since.
http://demographics.coopercenter.org/DotMap/ (an amazing map)
Happy to be corrected on anything, but that is what my research and the cited sources taught me...
/tangent