I just about remember the 90 (I think it was) from Bracknell to Reading, in terms of 2000s First Berks, but I didn't regularly go east out of Reading except to London until around 2015.
It depends when - it all changed a number of times in the 2000s / 2010s before First withdrew.
Early to mid 2000's, there were a group of routes on the Reading - Wokingham corridor -
190 was Reading - Bracknell (this may just have been evening and Sunday) reasonably direct (and I seem to remember Courtney did the Sunday service at one point - possibly under contract to Wokingham Council, and that may just have been Reading - Wokingham.)
191 was Reading - Bracknell - Ascot - Windsor - Slough
192 was Reading - Bracknell - Ascot (think there may have been some journeys - possibly round school times - through to Sunningdale)
193 was Reading - Wokingham - Camberley, buses generally worked a cycle of 193 Reading - Camberley then 194 Camberley - Bracknell and vice versa, so that drivers got back to Bracknell for breaks / change overs.
They ran as a regular (on paper at least) 20 minute headway at the Reading end.
The routes between Winnersh and Bracknell varied, with one serving Emmbrook, and at least one went in to Bracknell via Binfield, I think another went round some of the 'southern estates' in Bracknell. These in turn provided part of an even headway with a town service. I can't remember the exact details now, and don't have anything to hand with the detail.
I believe at a slightly earlier stage one or two of the routes got even further east, including to Heathrow (presumably via Slough) I have seen photographs of this but don't remember it (my involvement with the area started in the early 00's)
Then at some point the 190 was re-launched (with refurbished ex First London double deckers) as just Reading - Bracknell with a standard route, some areas lost their direct bus to Reading, some areas gained one (at the price of a convoluted 190 route) as the 190 also replaced a local service (196?) that didn't run west of Wokingham. 191 and 192 were cut back so as not to run west of Bracknell.
Then a bit later - after having made an effort to market the 190 as a brand - it turned in to the 90, and at one stage had two different lines of route (both under route number 90) between Wokingham and Bracknell - these turned in the 4 / X4 under Reading Buses, although I think the 4 now does a shorter loop in south Bracknell than it did at one time.