Caio Lucas hit the fortuitous winner seven minutes from time after Meloni scored with a 76th minute header to cancel out an own goal by Kouame Kouadio that gave Oman a 12th minute lead.
The win moves the UAE to the cusp of their first appearance at the World Cup since 1990 with Olaroiu's team only needing a draw away to Qatar on Tuesday to progress as winners of Group A in the fourth phase of Asia's preliminaries.
The Omanis threatened in the early exchanges when Issam Al-Sabhi stole possession inside the UAE half only for the attack to fizzle out when his shot was eventually blocked. Later on Carlos Queiroz's side had taken the lead.
With 14 minutes remaining the UAE deservedly pulled level, Meloni rising highest to meet substitute Ali Saleh's inswinging cross from the left to beat Al-Mukhaini. Seven minutes later Caio Lucas scored the winner.