The 25-year-old midfielder missed the 2-1 defeat at Brentford on Saturday with a calf strain, but will be handed a late fitness test. Scott McGleish will retain his place if Dawson fails to recover in time.
Defensive duo Ben Chorley and Jason Crowe remain doubtful with knee and ankle injuries respectively.
On-loan Tottenham striker Harry Kane is pushing for a recall along with fellow forward Jonathan Tehoue, midfielder Paul-Jose Mpoku and defender Terrell Forbes.
The O's will be looking to get back to winning ways after Brentford ended their 14-game unbeaten run.
Source: PA
Source: PA