With car off, press MPH/KPH button and hold while pressing brake and Power button to start. A screen will appear showing progress toward resettng oil maintenance reminder. When complete the screen will disappear and you can release the MPH/KPH button.
http://www.toyota.com/t3Portal/document/om/OM47685U/pdf/sec_04_03.pdf page 13 of the PDF, Page 440 of the manual After changing the engine oil (U.S.A. only) The oil change system should be reset. Perform the following steps: Turn the “POWER” switch OFF with the trip meter A shown. Turn the “POWER” switch ON with the MPH or km/h button (→P. 185) held down. Keep pressing the button until the trip meter indicates “000000” and the multi-information display indicates that the reset is complete.